OBG Management

In this article, I provide a simplified, practical review of the principal antibiotics that we use on a daily basis to treat bacterial infections. The antibiotics are listed in alphabetical order, either individually or by group. I focus first on the mechanism of action and spectrum of activity of the drugs used against the usual pelvic pathogens (TABLE).¹ I then review their principal adverse effects, relative cost (categorized as low, intermediate, and high), and the key indications for these drugs in obstetrics and gynecology. In a forthcoming 2-part companion article, I will review how to select specific antibiotics and their dosing regimens for the most commonly encountered bacterial infections in our clinical practice.

Aminoglycoside antibiotics

The aminoglycosides include amikacin, gentamicin, plazomicin, and tobramycin.^2,3 The 2 agents most commonly used in our specialty are amikacin and gentamicin. The drugs may be administered intramuscularly or intravenously, and they specifically target aerobic gram-negative bacilli. They also provide coverage against staphylococci and gonococci. Ototoxicity and nephrotoxicity are their principal adverse effects.

Aminoglycosides are used primarily as single agents to treat pyelonephritis caused by highly resistant bacteria and in combination with agents such as clindamycin and metronidazole to treat polymicrobial infections, including chorioamnionitis, puerperal endometritis, and pelvic inflammatory disease. Of all the aminoglycosides, gentamicin is clearly the least expensive.

Carbapenems

The original carbapenem widely introduced into clinical practice was imipenem-cilastatin. Imipenem, the active antibiotic, inhibits bacterial cell wall synthesis. Cilastatin inhibits renal dehydropeptidase I and, thereby, slows the metabolism of imipenem by the kidney. Other carbapenems include meropenem and ertapenem.

The carbapenems have the widest spectrum of activity against the pelvic pathogens of any antibiotic. They provide excellent coverage of aerobic and anaerobic gram-positive cocci and aerobic and anaerobic gram-negative bacilli. They do not cover methicillin-resistant Staphylococcus aureus (MRSA) and the enterococci very well.

A major adverse effect of the carbapenems is an allergic reaction, including anaphylaxis and Stevens-Johnson syndrome, and there is some minimal cross-sensitivity with the β-lactam antibiotics. Other important, but fortunately rare, adverse effects include neurotoxicity, hepatotoxicity, and Clostridium difficile colitis.⁴

As a group, the carbapenems are relatively more expensive than most other agents. Their principal application in our specialty is for single-agent treatment of serious polymicrobial infections, such as puerperal endometritis, pelvic cellulitis, and pelvic abscess, especially in patients who have a contraindication to the use of combination antibiotic regimens that include an aminoglycoside.^1,2

Cephalosporins

The cephalosporins are β-lactam antibiotics that act by disrupting the synthesis of the bacterial cell wall. They may be administered orally, intramuscularly, and intravenously. The most common adverse effects associated with these agents are an allergic reaction, which can range from a mild rash to anaphylaxis and the Stevens-Johnson syndrome; central nervous system toxicity; and antibiotic-induced diarrhea, including C difficile colitis.^1,2,4

This group of antibiotics can be confusing because it includes so many agents, and their spectrum of activity varies. I find it helpful to think about the coverage of these agents as limited spectrum versus intermediate spectrum versus extended spectrum.

The limited-spectrum cephalosporin prototypes are cephalexin (oral administration) and cefazolin (parenteral administration). This group of cephalosporins provides excellent coverage of aerobic and anaerobic gram-positive cocci. They are excellent against staphylococci, except for MRSA. Coverage is moderate for aerobic gram-negative bacilli but only limited for anaerobic gram-negative bacilli. They do not cover the enterococci. In our specialty, their principal application is for treatment of mastitis, urinary tract infections (UTIs), and wound infections and for prophylaxis against group B streptococcus (GBS) infection and post-cesarean infection.^2,5 The cost of these drugs is relatively low.

The prototypes of the intermediate-spectrum cephalosporins are cefixime (oral) and ceftriaxone (parenteral). Both drugs have strong activity against aerobic and anaerobic streptococci, Neisseria gonorrhoeae, most aerobic gram-negative bacilli, and Treponema pallidum (principally, ceftriaxone). They are not consistently effective against staphylococci, particularly MRSA, and enterococci. Their key indications in obstetrics and gynecology are treatment of gonorrhea, syphilis (in penicillin-allergic patients), and acute pyelonephritis. Compared with the limited-spectrum cephalosporins, these antibiotics are moderately expensive.^1,2

The 3 extended-spectrum cephalosporins used most commonly in our specialty are cefepime, cefotetan, and cefoxitin. These agents are administered intramuscularly and intravenously, and they provide very good coverage against aerobic and anaerobic gram-positive cocci, with the exception of staphylococci and enterococci. They have very good coverage against most gram-negative aerobic bacilli and excellent coverage against anerobic microorganisms. Their primary application in our specialty is for single-agent treatment of polymicrobial infections, such as puerperal endometritis and pelvic cellulitis. When used in combination with doxycycline, they are valuable in treating pelvic inflammatory disease. These drugs are more expensive than the limited-spectrum or intermediate-spectrum agents. They should not be used routinely as prophylaxis for pelvic surgery.^1,2,5

Continue to: Fluorinated quinolones...

Fluorinated quinolones

The fluorinated quinolones include several agents, but the 3 most commonly used in our specialty are ciprofloxacin, ofloxacin, and levofloxacin. All 3 drugs can be administered orally; ciprofloxacin and levofloxacin also are available in intravenous formulations. These drugs interfere with bacterial protein synthesis by targeting DNA gyrase, an enzyme that introduces negative supertwists into DNA and separates interlocked DNA molecules.

These drugs provide excellent coverage against gram-negative bacilli, including Haemophilus influenzae; gram-negative cocci, such as N gonorrhoeae, Neisseria meningitidis, and Moraxella catarrhalis; and many staphylococci species. Levofloxacin, but not the other 2 drugs, provides moderate coverage against anaerobes. Ofloxacin and levofloxacin are active against chlamydia. Levofloxacin also covers the mycoplasma organisms that are responsible for atypical pneumonia.

As a group, the fluorinated quinolones are moderately expensive. The most likely adverse effects with these agents are gastrointestinal (GI) upset, headache, agitation, and sleep disturbance. Allergic reactions are rare. These drugs are of primary value in our specialty in treating gonorrhea, chlamydia, complicated UTIs, and respiratory tract infections.^1,2,6

The penicillins

Penicillin

Penicillin, a β-lactam antibiotic, was one of the first antibiotics developed and employed in clinical practice. It may be administered orally, intramuscularly, and intravenously. Penicillin exerts its effect by interfering with bacterial cell wall synthesis. Its principal spectrum of activity is against aerobic streptococci, such as group A and B streptococcus; most anaerobic gram-positive cocci that are present in the vaginal flora; some anaerobic gram-negative bacilli; and T pallidum. Penicillin is not effective against the majority of staphylococci species, enterococci, or aerobic gram-negative bacilli, such as Escherichia coli.

Penicillin’s major adverse effect is an allergic reaction, experienced by less than 10% of recipients.⁷ Most reactions are mild and are characterized by a morbilliform skin rash. However, some reactions are severe and take the form of an urticarial skin eruption, laryngospasm, bronchospasm, and overt anaphylaxis. The cost of both oral and parenteral penicillin formulations is very low. In obstetrics and gynecology, penicillin is used primarily for the treatment of group A and B streptococci infections, clostridial infections, and syphilis.^1,2

Ampicillin and amoxicillin

The β-lactam antibiotics ampicillin and amoxicillin also act by interfering with bacterial cell wall synthesis. Amoxicillin is administered orally; ampicillin may be administered orally, intramuscularly, and intravenously. Their spectrum of activity includes group A and B streptococci, enterococci, most anaerobic gram-positive cocci, some anaerobic gram-negative bacilli, many aerobic gram-negative bacilli, and clostridial organisms.

Like penicillin, ampicillin and amoxicillin may cause allergic reactions that range from mild rashes to anaphylaxis. Unlike the more narrow-spectrum penicillin, they may cause antibiotic-associated diarrhea, including C difficile colitis,⁴ and they may eliminate part of the normal vaginal flora and stimulate an overgrowth of yeast organisms in the vagina. The cost of ampicillin and amoxicillin is very low. These 2 agents are used primarily for treatment of group A and B streptococci infections and some UTIs, particularly those caused by enterococci.^1,2

Dicloxacillin sodium

This penicillin derivative disrupts bacterial cell wall synthesis and targets primarily aerobic gram-positive cocci, particularly staphylococci species. The antibiotic is not active against MRSA. The principal adverse effects of dicloxacillin sodium are an allergic reaction and GI upset. The drug is very inexpensive.

The key application for dicloxacillin sodium in our specialty is for treatment of puerperal mastitis.¹

Continue to: Extended-spectrum penicillins...

Three interesting combination extended-spectrum penicillins are used widely in our specialty. They are ampicillin/sulbactam, amoxicillin/clavulanate, and piperacillin/tazobactam. Ampicillin/sulbactam may be administered intramuscularly and intravenously. Piperacillin/tazobactam is administered intravenously; amoxicillin/clavulanate is administered orally.

Clavulanate, sulbactam, and tazobactam are β-lactamase inhibitors. When added to the parent antibiotic (amoxicillin, ampicillin, and piperacillin, respectively), they significantly enhance the parent drug’s spectrum of activity. These agents interfere with bacterial cell wall synthesis. They provide excellent coverage of aerobic gram-positive cocci, including enterococci; anaerobic gram-positive cocci; anaerobic gram-negative bacilli; and aerobic gram-negative bacilli. Their principal adverse effects include allergic reactions and antibiotic-associated diarrhea. They are moderately expensive.

The principal application of ampicillin/sulbactam and piperacillin/tazobactam in our specialty is as single agents for treatment of puerperal endometritis, postoperative pelvic cellulitis, and pyelonephritis. The usual role for amoxicillin/clavulanate is for oral treatment of complicated UTIs, including pyelonephritis in early pregnancy, and for outpatient therapy of mild to moderately severe endometritis following delivery or pregnancy termination.

Macrolides, monobactams, and additional antibiotics

Azithromycin

Azithromycin is a macrolide antibiotic that is in the same class as erythromycin and clindamycin. In our specialty, it has largely replaced erythromycin because of its more convenient dosage schedule and its better tolerability. It inhibits bacterial protein synthesis, and it is available in both an oral and intravenous formulation.

Azithromycin has an excellent spectrum of activity against the 3 major microorganisms that cause otitis media, sinusitis, and bronchitis: Streptococcus pneumoniae, H influenzae, and M catarrhalis. It also provides excellent coverage of Chlamydia trachomatis, Mycoplasma pneumoniae, and genital mycoplasmas; in high doses it provides modest coverage against gonorrhea.⁸ Unlike erythromycin, it has minimal GI toxicity and is usually very well tolerated by most patients. One unusual, but very important, adverse effect of the drug is prolongation of the Q-T interval.⁹

Azithromycin is now available in generic form and is relatively inexpensive. As a single agent, its principal applications in our specialty are for treatment of respiratory tract infections such as otitis media, sinusitis, and acute bronchitis and for treatment of chlamydia urethritis and endocervicitis.^8,10 In combination with ampicillin, azithromycin is used as prophylaxis in patients with preterm premature rupture of membranes (PPROM), and, in combination with cefazolin, it is used for prophylaxis in patients undergoing cesarean delivery.^1,2,5

Aztreonam

Aztreonam is a monobactam antibiotic. Like the cephalosporins and penicillins, aztreonam inhibits bacterial cell wall synthesis. It may be administered intramuscularly and intravenously, and its principal spectrum of activity is against aerobic gram-negative bacilli, which is similar to the aminoglycosides’ spectrum.

Aztreonam’s most likely adverse effects include phlebitis at the injection site, allergy, GI upset, and diarrhea. The drug is moderately expensive. In our specialty, aztreonam could be used as a single agent, in lieu of an aminoglycoside, for treatment of pyelonephritis caused by an unusually resistant organism. It also could be used in combination with clindamycin or metronidazole plus ampicillin for treatment of polymicrobial infections, such as chorioamnionitis, puerperal endometritis, and pelvic cellulitis.^1,2

Continue to: Clindamycin...

Clindamycin

A macrolide antibiotic, clindamycin exerts its antibacterial effect by interfering with bacterial protein synthesis. It can be administered orally and intravenously. Its key spectrum of activity in our specialty includes GBS, staphylococci, and anaerobes. However, clindamycin is not active against enterococci or aerobic gram-negative bacilli. GI upset and antibiotic-induced diarrhea are its principal adverse effects, and clindamycin is one of the most important causes of C difficile colitis. Although it is available in a generic formulation, this drug is still relatively expensive.

Clindamycin’s principal application in our specialty is for treating staphylococcal infections, such as wound infections and mastitis. It is particularly effective against MRSA infections. When used in combination with an aminoglycoside such as gentamicin, clindamycin provides excellent treatment for chorioamnionitis, puerperal endometritis, and pelvic inflammatory disease. In fact, for many years, the combination of clindamycin plus gentamicin has been considered the gold standard for the treatment of polymicrobial, mixed aerobic-anaerobic pelvic infections.^1,2

Doxycycline

Doxycycline, a tetracycline, exerts its antibacterial effect by inhibiting bacterial protein synthesis. The drug targets a broad range of pelvic pathogens, including C trachomatis and N gonorrhoeae, and it may be administered both orally and intravenously. Doxycycline’s principal adverse effects include headache, GI upset, and photosensitivity. By disrupting the normal bowel and vaginal flora, the drug also can cause diarrhea and vulvovaginal moniliasis. In addition, it can cause permanent discoloration of the teeth, and, for this reason, doxycycline should not be used in pregnant or lactating women or in young children.

Although doxycycline has been available in generic formulation for many years, it remains relatively expensive. As a single agent, its principal application in our specialty is for treatment of chlamydia infection. It may be used as prophylaxis for surgical procedures, such as hysterectomy and pregnancy terminations. In combination with an extended-spectrum cephalosporin, it also may be used to treat pelvic inflammatory disease.^2,8,10

Metronidazole

Metronidazole, a nitroimidazole derivative, exerts its antibacterial effect by disrupting bacterial protein synthesis. The drug may be administered topically, orally, and intravenously. Its primary spectrum of activity is against anerobic microorganisms. It is also active against Giardia and Trichomonas vaginalis.

Metronidazole’s most common adverse effects are GI upset, a metallic taste in the mouth, and a disulfiram-like effect when taken with alcohol. The cost of oral and intravenous metronidazole is relatively low; ironically, the cost of topical metronidazole is relatively high. In our specialty, the principal applications of oral metronidazole are as a single agent for treatment of bacterial vaginosis and trichomoniasis. When combined with ampicillin plus an aminoglycoside, intravenous metronidazole provides excellent coverage against the diverse anaerobic microorganisms that cause chorioamnionitis, puerperal endometritis, and pelvic cellulitis.^1,2

Trimethoprim-sulfamethoxazole (TMP-SMX)

This antibiotic combination (an antifolate and a sulfonamide) inhibits sequential steps in the synthesis of folic acid, an essential nutrient in bacterial metabolism. It is available in both an intravenous and oral formulation. TMP-SMX has a broad spectrum of activity against the aerobic gram-negative bacilli that cause UTIs in women. In addition, it provides excellent coverage against staphylococci, including MRSA; Pneumocystis jirovecii; and Toxoplasma gondii.

The medication’s principal toxicity is an allergic reaction. Some reactions are quite severe, such as the Stevens-Johnson syndrome. TMP-SMX is relatively inexpensive, particularly the oral formulation. The most common indications for TMP-SMX in our specialty are for treatment of UTIs, mastitis, and wound infections.^1,2,11 In HIV-infected patients, the drug provides excellent prophylaxis against recurrent Pneumocystis and Toxoplasma infections. TMP-SMX should not be used in the first trimester of pregnancy because it has been linked to several birth defects, including neural tube defects, heart defects, choanal atresia, and diaphragmatic hernia.¹²

Nitrofurantoin

Usually administered orally as nitrofurantoin monohydrate macrocrystals, nitrofurantoin exerts its antibacterial effect primarily by inhibiting protein synthesis. Its principal spectrum of activity is against the aerobic gram-negative bacilli, with the exception of Proteus species. Nitrofurantoin’s most common adverse effects are GI upset, headache, vertigo, drowsiness, and allergic reactions. The drug is relatively inexpensive.

Nitrofurantoin is an excellent agent for the treatment of lower UTIs.¹¹ It is not well concentrated in the renal parenchyma or blood, however, so it should not be used to treat pyelonephritis. As a general rule, nitrofurantoin should not be used in the first trimester of pregnancy because it has been associated with eye, heart, and facial cleft defects in the fetus.¹²

Vancomycin

Vancomycin exerts its antibacterial effect by inhibiting cell wall synthesis. It may be administered both orally and intravenously, and it specifically targets aerobic gram-positive cocci, particularly methicillin-sensitive and methicillin-resistant staphylococci. Vancomycin’s most important adverse effects include GI upset, nephrotoxicity, ototoxicity, and severe allergic reactions, such as anaphylaxis, Stevens-Johnson syndrome, and exfoliative dermatitis (the “red man” syndrome). The drug is moderately expensive.¹³

In its oral formulation, vancomycin’s principal application in our discipline is for treating C difficile colitis. In its intravenous formulation, it is used primarily as a single agent for GBS prophylaxis in penicillin-allergic patients, and it is used in combination with other antibiotics, such as clindamycin plus gentamicin, for treating patients with deep-seated incisional (wound) infections.^1,2,13,14 ●

In this article, I provide a simplified, practical review of the principal antibiotics that we use on a daily basis to treat bacterial infections. The antibiotics are listed in alphabetical order, either individually or by group. I focus first on the mechanism of action and spectrum of activity of the drugs used against the usual pelvic pathogens (TABLE).¹ I then review their principal adverse effects, relative cost (categorized as low, intermediate, and high), and the key indications for these drugs in obstetrics and gynecology. In a forthcoming 2-part companion article, I will review how to select specific antibiotics and their dosing regimens for the most commonly encountered bacterial infections in our clinical practice.

Aminoglycoside antibiotics

The aminoglycosides include amikacin, gentamicin, plazomicin, and tobramycin.^2,3 The 2 agents most commonly used in our specialty are amikacin and gentamicin. The drugs may be administered intramuscularly or intravenously, and they specifically target aerobic gram-negative bacilli. They also provide coverage against staphylococci and gonococci. Ototoxicity and nephrotoxicity are their principal adverse effects.

Aminoglycosides are used primarily as single agents to treat pyelonephritis caused by highly resistant bacteria and in combination with agents such as clindamycin and metronidazole to treat polymicrobial infections, including chorioamnionitis, puerperal endometritis, and pelvic inflammatory disease. Of all the aminoglycosides, gentamicin is clearly the least expensive.

Carbapenems

The original carbapenem widely introduced into clinical practice was imipenem-cilastatin. Imipenem, the active antibiotic, inhibits bacterial cell wall synthesis. Cilastatin inhibits renal dehydropeptidase I and, thereby, slows the metabolism of imipenem by the kidney. Other carbapenems include meropenem and ertapenem.

The carbapenems have the widest spectrum of activity against the pelvic pathogens of any antibiotic. They provide excellent coverage of aerobic and anaerobic gram-positive cocci and aerobic and anaerobic gram-negative bacilli. They do not cover methicillin-resistant Staphylococcus aureus (MRSA) and the enterococci very well.

A major adverse effect of the carbapenems is an allergic reaction, including anaphylaxis and Stevens-Johnson syndrome, and there is some minimal cross-sensitivity with the β-lactam antibiotics. Other important, but fortunately rare, adverse effects include neurotoxicity, hepatotoxicity, and Clostridium difficile colitis.⁴

As a group, the carbapenems are relatively more expensive than most other agents. Their principal application in our specialty is for single-agent treatment of serious polymicrobial infections, such as puerperal endometritis, pelvic cellulitis, and pelvic abscess, especially in patients who have a contraindication to the use of combination antibiotic regimens that include an aminoglycoside.^1,2

Cephalosporins

The cephalosporins are β-lactam antibiotics that act by disrupting the synthesis of the bacterial cell wall. They may be administered orally, intramuscularly, and intravenously. The most common adverse effects associated with these agents are an allergic reaction, which can range from a mild rash to anaphylaxis and the Stevens-Johnson syndrome; central nervous system toxicity; and antibiotic-induced diarrhea, including C difficile colitis.^1,2,4

This group of antibiotics can be confusing because it includes so many agents, and their spectrum of activity varies. I find it helpful to think about the coverage of these agents as limited spectrum versus intermediate spectrum versus extended spectrum.

The limited-spectrum cephalosporin prototypes are cephalexin (oral administration) and cefazolin (parenteral administration). This group of cephalosporins provides excellent coverage of aerobic and anaerobic gram-positive cocci. They are excellent against staphylococci, except for MRSA. Coverage is moderate for aerobic gram-negative bacilli but only limited for anaerobic gram-negative bacilli. They do not cover the enterococci. In our specialty, their principal application is for treatment of mastitis, urinary tract infections (UTIs), and wound infections and for prophylaxis against group B streptococcus (GBS) infection and post-cesarean infection.^2,5 The cost of these drugs is relatively low.

The prototypes of the intermediate-spectrum cephalosporins are cefixime (oral) and ceftriaxone (parenteral). Both drugs have strong activity against aerobic and anaerobic streptococci, Neisseria gonorrhoeae, most aerobic gram-negative bacilli, and Treponema pallidum (principally, ceftriaxone). They are not consistently effective against staphylococci, particularly MRSA, and enterococci. Their key indications in obstetrics and gynecology are treatment of gonorrhea, syphilis (in penicillin-allergic patients), and acute pyelonephritis. Compared with the limited-spectrum cephalosporins, these antibiotics are moderately expensive.^1,2

The 3 extended-spectrum cephalosporins used most commonly in our specialty are cefepime, cefotetan, and cefoxitin. These agents are administered intramuscularly and intravenously, and they provide very good coverage against aerobic and anaerobic gram-positive cocci, with the exception of staphylococci and enterococci. They have very good coverage against most gram-negative aerobic bacilli and excellent coverage against anerobic microorganisms. Their primary application in our specialty is for single-agent treatment of polymicrobial infections, such as puerperal endometritis and pelvic cellulitis. When used in combination with doxycycline, they are valuable in treating pelvic inflammatory disease. These drugs are more expensive than the limited-spectrum or intermediate-spectrum agents. They should not be used routinely as prophylaxis for pelvic surgery.^1,2,5

Continue to: Fluorinated quinolones...

Fluorinated quinolones

The fluorinated quinolones include several agents, but the 3 most commonly used in our specialty are ciprofloxacin, ofloxacin, and levofloxacin. All 3 drugs can be administered orally; ciprofloxacin and levofloxacin also are available in intravenous formulations. These drugs interfere with bacterial protein synthesis by targeting DNA gyrase, an enzyme that introduces negative supertwists into DNA and separates interlocked DNA molecules.

These drugs provide excellent coverage against gram-negative bacilli, including Haemophilus influenzae; gram-negative cocci, such as N gonorrhoeae, Neisseria meningitidis, and Moraxella catarrhalis; and many staphylococci species. Levofloxacin, but not the other 2 drugs, provides moderate coverage against anaerobes. Ofloxacin and levofloxacin are active against chlamydia. Levofloxacin also covers the mycoplasma organisms that are responsible for atypical pneumonia.

As a group, the fluorinated quinolones are moderately expensive. The most likely adverse effects with these agents are gastrointestinal (GI) upset, headache, agitation, and sleep disturbance. Allergic reactions are rare. These drugs are of primary value in our specialty in treating gonorrhea, chlamydia, complicated UTIs, and respiratory tract infections.^1,2,6

The penicillins

Penicillin

Penicillin, a β-lactam antibiotic, was one of the first antibiotics developed and employed in clinical practice. It may be administered orally, intramuscularly, and intravenously. Penicillin exerts its effect by interfering with bacterial cell wall synthesis. Its principal spectrum of activity is against aerobic streptococci, such as group A and B streptococcus; most anaerobic gram-positive cocci that are present in the vaginal flora; some anaerobic gram-negative bacilli; and T pallidum. Penicillin is not effective against the majority of staphylococci species, enterococci, or aerobic gram-negative bacilli, such as Escherichia coli.

Penicillin’s major adverse effect is an allergic reaction, experienced by less than 10% of recipients.⁷ Most reactions are mild and are characterized by a morbilliform skin rash. However, some reactions are severe and take the form of an urticarial skin eruption, laryngospasm, bronchospasm, and overt anaphylaxis. The cost of both oral and parenteral penicillin formulations is very low. In obstetrics and gynecology, penicillin is used primarily for the treatment of group A and B streptococci infections, clostridial infections, and syphilis.^1,2

Ampicillin and amoxicillin

The β-lactam antibiotics ampicillin and amoxicillin also act by interfering with bacterial cell wall synthesis. Amoxicillin is administered orally; ampicillin may be administered orally, intramuscularly, and intravenously. Their spectrum of activity includes group A and B streptococci, enterococci, most anaerobic gram-positive cocci, some anaerobic gram-negative bacilli, many aerobic gram-negative bacilli, and clostridial organisms.

Like penicillin, ampicillin and amoxicillin may cause allergic reactions that range from mild rashes to anaphylaxis. Unlike the more narrow-spectrum penicillin, they may cause antibiotic-associated diarrhea, including C difficile colitis,⁴ and they may eliminate part of the normal vaginal flora and stimulate an overgrowth of yeast organisms in the vagina. The cost of ampicillin and amoxicillin is very low. These 2 agents are used primarily for treatment of group A and B streptococci infections and some UTIs, particularly those caused by enterococci.^1,2

Dicloxacillin sodium

This penicillin derivative disrupts bacterial cell wall synthesis and targets primarily aerobic gram-positive cocci, particularly staphylococci species. The antibiotic is not active against MRSA. The principal adverse effects of dicloxacillin sodium are an allergic reaction and GI upset. The drug is very inexpensive.

The key application for dicloxacillin sodium in our specialty is for treatment of puerperal mastitis.¹

Continue to: Extended-spectrum penicillins...

Three interesting combination extended-spectrum penicillins are used widely in our specialty. They are ampicillin/sulbactam, amoxicillin/clavulanate, and piperacillin/tazobactam. Ampicillin/sulbactam may be administered intramuscularly and intravenously. Piperacillin/tazobactam is administered intravenously; amoxicillin/clavulanate is administered orally.

Clavulanate, sulbactam, and tazobactam are β-lactamase inhibitors. When added to the parent antibiotic (amoxicillin, ampicillin, and piperacillin, respectively), they significantly enhance the parent drug’s spectrum of activity. These agents interfere with bacterial cell wall synthesis. They provide excellent coverage of aerobic gram-positive cocci, including enterococci; anaerobic gram-positive cocci; anaerobic gram-negative bacilli; and aerobic gram-negative bacilli. Their principal adverse effects include allergic reactions and antibiotic-associated diarrhea. They are moderately expensive.

The principal application of ampicillin/sulbactam and piperacillin/tazobactam in our specialty is as single agents for treatment of puerperal endometritis, postoperative pelvic cellulitis, and pyelonephritis. The usual role for amoxicillin/clavulanate is for oral treatment of complicated UTIs, including pyelonephritis in early pregnancy, and for outpatient therapy of mild to moderately severe endometritis following delivery or pregnancy termination.

Macrolides, monobactams, and additional antibiotics

Azithromycin

Azithromycin is a macrolide antibiotic that is in the same class as erythromycin and clindamycin. In our specialty, it has largely replaced erythromycin because of its more convenient dosage schedule and its better tolerability. It inhibits bacterial protein synthesis, and it is available in both an oral and intravenous formulation.

Azithromycin has an excellent spectrum of activity against the 3 major microorganisms that cause otitis media, sinusitis, and bronchitis: Streptococcus pneumoniae, H influenzae, and M catarrhalis. It also provides excellent coverage of Chlamydia trachomatis, Mycoplasma pneumoniae, and genital mycoplasmas; in high doses it provides modest coverage against gonorrhea.⁸ Unlike erythromycin, it has minimal GI toxicity and is usually very well tolerated by most patients. One unusual, but very important, adverse effect of the drug is prolongation of the Q-T interval.⁹

Azithromycin is now available in generic form and is relatively inexpensive. As a single agent, its principal applications in our specialty are for treatment of respiratory tract infections such as otitis media, sinusitis, and acute bronchitis and for treatment of chlamydia urethritis and endocervicitis.^8,10 In combination with ampicillin, azithromycin is used as prophylaxis in patients with preterm premature rupture of membranes (PPROM), and, in combination with cefazolin, it is used for prophylaxis in patients undergoing cesarean delivery.^1,2,5

Aztreonam

Aztreonam is a monobactam antibiotic. Like the cephalosporins and penicillins, aztreonam inhibits bacterial cell wall synthesis. It may be administered intramuscularly and intravenously, and its principal spectrum of activity is against aerobic gram-negative bacilli, which is similar to the aminoglycosides’ spectrum.

Aztreonam’s most likely adverse effects include phlebitis at the injection site, allergy, GI upset, and diarrhea. The drug is moderately expensive. In our specialty, aztreonam could be used as a single agent, in lieu of an aminoglycoside, for treatment of pyelonephritis caused by an unusually resistant organism. It also could be used in combination with clindamycin or metronidazole plus ampicillin for treatment of polymicrobial infections, such as chorioamnionitis, puerperal endometritis, and pelvic cellulitis.^1,2

Continue to: Clindamycin...

Clindamycin

A macrolide antibiotic, clindamycin exerts its antibacterial effect by interfering with bacterial protein synthesis. It can be administered orally and intravenously. Its key spectrum of activity in our specialty includes GBS, staphylococci, and anaerobes. However, clindamycin is not active against enterococci or aerobic gram-negative bacilli. GI upset and antibiotic-induced diarrhea are its principal adverse effects, and clindamycin is one of the most important causes of C difficile colitis. Although it is available in a generic formulation, this drug is still relatively expensive.

Clindamycin’s principal application in our specialty is for treating staphylococcal infections, such as wound infections and mastitis. It is particularly effective against MRSA infections. When used in combination with an aminoglycoside such as gentamicin, clindamycin provides excellent treatment for chorioamnionitis, puerperal endometritis, and pelvic inflammatory disease. In fact, for many years, the combination of clindamycin plus gentamicin has been considered the gold standard for the treatment of polymicrobial, mixed aerobic-anaerobic pelvic infections.^1,2

Doxycycline

Doxycycline, a tetracycline, exerts its antibacterial effect by inhibiting bacterial protein synthesis. The drug targets a broad range of pelvic pathogens, including C trachomatis and N gonorrhoeae, and it may be administered both orally and intravenously. Doxycycline’s principal adverse effects include headache, GI upset, and photosensitivity. By disrupting the normal bowel and vaginal flora, the drug also can cause diarrhea and vulvovaginal moniliasis. In addition, it can cause permanent discoloration of the teeth, and, for this reason, doxycycline should not be used in pregnant or lactating women or in young children.

Although doxycycline has been available in generic formulation for many years, it remains relatively expensive. As a single agent, its principal application in our specialty is for treatment of chlamydia infection. It may be used as prophylaxis for surgical procedures, such as hysterectomy and pregnancy terminations. In combination with an extended-spectrum cephalosporin, it also may be used to treat pelvic inflammatory disease.^2,8,10

Metronidazole

Metronidazole, a nitroimidazole derivative, exerts its antibacterial effect by disrupting bacterial protein synthesis. The drug may be administered topically, orally, and intravenously. Its primary spectrum of activity is against anerobic microorganisms. It is also active against Giardia and Trichomonas vaginalis.

Metronidazole’s most common adverse effects are GI upset, a metallic taste in the mouth, and a disulfiram-like effect when taken with alcohol. The cost of oral and intravenous metronidazole is relatively low; ironically, the cost of topical metronidazole is relatively high. In our specialty, the principal applications of oral metronidazole are as a single agent for treatment of bacterial vaginosis and trichomoniasis. When combined with ampicillin plus an aminoglycoside, intravenous metronidazole provides excellent coverage against the diverse anaerobic microorganisms that cause chorioamnionitis, puerperal endometritis, and pelvic cellulitis.^1,2

Trimethoprim-sulfamethoxazole (TMP-SMX)

This antibiotic combination (an antifolate and a sulfonamide) inhibits sequential steps in the synthesis of folic acid, an essential nutrient in bacterial metabolism. It is available in both an intravenous and oral formulation. TMP-SMX has a broad spectrum of activity against the aerobic gram-negative bacilli that cause UTIs in women. In addition, it provides excellent coverage against staphylococci, including MRSA; Pneumocystis jirovecii; and Toxoplasma gondii.

The medication’s principal toxicity is an allergic reaction. Some reactions are quite severe, such as the Stevens-Johnson syndrome. TMP-SMX is relatively inexpensive, particularly the oral formulation. The most common indications for TMP-SMX in our specialty are for treatment of UTIs, mastitis, and wound infections.^1,2,11 In HIV-infected patients, the drug provides excellent prophylaxis against recurrent Pneumocystis and Toxoplasma infections. TMP-SMX should not be used in the first trimester of pregnancy because it has been linked to several birth defects, including neural tube defects, heart defects, choanal atresia, and diaphragmatic hernia.¹²

Nitrofurantoin

Usually administered orally as nitrofurantoin monohydrate macrocrystals, nitrofurantoin exerts its antibacterial effect primarily by inhibiting protein synthesis. Its principal spectrum of activity is against the aerobic gram-negative bacilli, with the exception of Proteus species. Nitrofurantoin’s most common adverse effects are GI upset, headache, vertigo, drowsiness, and allergic reactions. The drug is relatively inexpensive.

Nitrofurantoin is an excellent agent for the treatment of lower UTIs.¹¹ It is not well concentrated in the renal parenchyma or blood, however, so it should not be used to treat pyelonephritis. As a general rule, nitrofurantoin should not be used in the first trimester of pregnancy because it has been associated with eye, heart, and facial cleft defects in the fetus.¹²

Vancomycin

Vancomycin exerts its antibacterial effect by inhibiting cell wall synthesis. It may be administered both orally and intravenously, and it specifically targets aerobic gram-positive cocci, particularly methicillin-sensitive and methicillin-resistant staphylococci. Vancomycin’s most important adverse effects include GI upset, nephrotoxicity, ototoxicity, and severe allergic reactions, such as anaphylaxis, Stevens-Johnson syndrome, and exfoliative dermatitis (the “red man” syndrome). The drug is moderately expensive.¹³

In its oral formulation, vancomycin’s principal application in our discipline is for treating C difficile colitis. In its intravenous formulation, it is used primarily as a single agent for GBS prophylaxis in penicillin-allergic patients, and it is used in combination with other antibiotics, such as clindamycin plus gentamicin, for treating patients with deep-seated incisional (wound) infections.^1,2,13,14 ●

In this article, I provide a simplified, practical review of the principal antibiotics that we use on a daily basis to treat bacterial infections. The antibiotics are listed in alphabetical order, either individually or by group. I focus first on the mechanism of action and spectrum of activity of the drugs used against the usual pelvic pathogens (TABLE).¹ I then review their principal adverse effects, relative cost (categorized as low, intermediate, and high), and the key indications for these drugs in obstetrics and gynecology. In a forthcoming 2-part companion article, I will review how to select specific antibiotics and their dosing regimens for the most commonly encountered bacterial infections in our clinical practice.

Aminoglycoside antibiotics

The aminoglycosides include amikacin, gentamicin, plazomicin, and tobramycin.^2,3 The 2 agents most commonly used in our specialty are amikacin and gentamicin. The drugs may be administered intramuscularly or intravenously, and they specifically target aerobic gram-negative bacilli. They also provide coverage against staphylococci and gonococci. Ototoxicity and nephrotoxicity are their principal adverse effects.

Aminoglycosides are used primarily as single agents to treat pyelonephritis caused by highly resistant bacteria and in combination with agents such as clindamycin and metronidazole to treat polymicrobial infections, including chorioamnionitis, puerperal endometritis, and pelvic inflammatory disease. Of all the aminoglycosides, gentamicin is clearly the least expensive.

Carbapenems

The original carbapenem widely introduced into clinical practice was imipenem-cilastatin. Imipenem, the active antibiotic, inhibits bacterial cell wall synthesis. Cilastatin inhibits renal dehydropeptidase I and, thereby, slows the metabolism of imipenem by the kidney. Other carbapenems include meropenem and ertapenem.

The carbapenems have the widest spectrum of activity against the pelvic pathogens of any antibiotic. They provide excellent coverage of aerobic and anaerobic gram-positive cocci and aerobic and anaerobic gram-negative bacilli. They do not cover methicillin-resistant Staphylococcus aureus (MRSA) and the enterococci very well.

A major adverse effect of the carbapenems is an allergic reaction, including anaphylaxis and Stevens-Johnson syndrome, and there is some minimal cross-sensitivity with the β-lactam antibiotics. Other important, but fortunately rare, adverse effects include neurotoxicity, hepatotoxicity, and Clostridium difficile colitis.⁴

As a group, the carbapenems are relatively more expensive than most other agents. Their principal application in our specialty is for single-agent treatment of serious polymicrobial infections, such as puerperal endometritis, pelvic cellulitis, and pelvic abscess, especially in patients who have a contraindication to the use of combination antibiotic regimens that include an aminoglycoside.^1,2

Cephalosporins

The cephalosporins are β-lactam antibiotics that act by disrupting the synthesis of the bacterial cell wall. They may be administered orally, intramuscularly, and intravenously. The most common adverse effects associated with these agents are an allergic reaction, which can range from a mild rash to anaphylaxis and the Stevens-Johnson syndrome; central nervous system toxicity; and antibiotic-induced diarrhea, including C difficile colitis.^1,2,4

This group of antibiotics can be confusing because it includes so many agents, and their spectrum of activity varies. I find it helpful to think about the coverage of these agents as limited spectrum versus intermediate spectrum versus extended spectrum.

The limited-spectrum cephalosporin prototypes are cephalexin (oral administration) and cefazolin (parenteral administration). This group of cephalosporins provides excellent coverage of aerobic and anaerobic gram-positive cocci. They are excellent against staphylococci, except for MRSA. Coverage is moderate for aerobic gram-negative bacilli but only limited for anaerobic gram-negative bacilli. They do not cover the enterococci. In our specialty, their principal application is for treatment of mastitis, urinary tract infections (UTIs), and wound infections and for prophylaxis against group B streptococcus (GBS) infection and post-cesarean infection.^2,5 The cost of these drugs is relatively low.

The prototypes of the intermediate-spectrum cephalosporins are cefixime (oral) and ceftriaxone (parenteral). Both drugs have strong activity against aerobic and anaerobic streptococci, Neisseria gonorrhoeae, most aerobic gram-negative bacilli, and Treponema pallidum (principally, ceftriaxone). They are not consistently effective against staphylococci, particularly MRSA, and enterococci. Their key indications in obstetrics and gynecology are treatment of gonorrhea, syphilis (in penicillin-allergic patients), and acute pyelonephritis. Compared with the limited-spectrum cephalosporins, these antibiotics are moderately expensive.^1,2

The 3 extended-spectrum cephalosporins used most commonly in our specialty are cefepime, cefotetan, and cefoxitin. These agents are administered intramuscularly and intravenously, and they provide very good coverage against aerobic and anaerobic gram-positive cocci, with the exception of staphylococci and enterococci. They have very good coverage against most gram-negative aerobic bacilli and excellent coverage against anerobic microorganisms. Their primary application in our specialty is for single-agent treatment of polymicrobial infections, such as puerperal endometritis and pelvic cellulitis. When used in combination with doxycycline, they are valuable in treating pelvic inflammatory disease. These drugs are more expensive than the limited-spectrum or intermediate-spectrum agents. They should not be used routinely as prophylaxis for pelvic surgery.^1,2,5

Continue to: Fluorinated quinolones...

Fluorinated quinolones

The fluorinated quinolones include several agents, but the 3 most commonly used in our specialty are ciprofloxacin, ofloxacin, and levofloxacin. All 3 drugs can be administered orally; ciprofloxacin and levofloxacin also are available in intravenous formulations. These drugs interfere with bacterial protein synthesis by targeting DNA gyrase, an enzyme that introduces negative supertwists into DNA and separates interlocked DNA molecules.

These drugs provide excellent coverage against gram-negative bacilli, including Haemophilus influenzae; gram-negative cocci, such as N gonorrhoeae, Neisseria meningitidis, and Moraxella catarrhalis; and many staphylococci species. Levofloxacin, but not the other 2 drugs, provides moderate coverage against anaerobes. Ofloxacin and levofloxacin are active against chlamydia. Levofloxacin also covers the mycoplasma organisms that are responsible for atypical pneumonia.

As a group, the fluorinated quinolones are moderately expensive. The most likely adverse effects with these agents are gastrointestinal (GI) upset, headache, agitation, and sleep disturbance. Allergic reactions are rare. These drugs are of primary value in our specialty in treating gonorrhea, chlamydia, complicated UTIs, and respiratory tract infections.^1,2,6

The penicillins

Penicillin

Penicillin, a β-lactam antibiotic, was one of the first antibiotics developed and employed in clinical practice. It may be administered orally, intramuscularly, and intravenously. Penicillin exerts its effect by interfering with bacterial cell wall synthesis. Its principal spectrum of activity is against aerobic streptococci, such as group A and B streptococcus; most anaerobic gram-positive cocci that are present in the vaginal flora; some anaerobic gram-negative bacilli; and T pallidum. Penicillin is not effective against the majority of staphylococci species, enterococci, or aerobic gram-negative bacilli, such as Escherichia coli.

Penicillin’s major adverse effect is an allergic reaction, experienced by less than 10% of recipients.⁷ Most reactions are mild and are characterized by a morbilliform skin rash. However, some reactions are severe and take the form of an urticarial skin eruption, laryngospasm, bronchospasm, and overt anaphylaxis. The cost of both oral and parenteral penicillin formulations is very low. In obstetrics and gynecology, penicillin is used primarily for the treatment of group A and B streptococci infections, clostridial infections, and syphilis.^1,2

Ampicillin and amoxicillin

The β-lactam antibiotics ampicillin and amoxicillin also act by interfering with bacterial cell wall synthesis. Amoxicillin is administered orally; ampicillin may be administered orally, intramuscularly, and intravenously. Their spectrum of activity includes group A and B streptococci, enterococci, most anaerobic gram-positive cocci, some anaerobic gram-negative bacilli, many aerobic gram-negative bacilli, and clostridial organisms.

Like penicillin, ampicillin and amoxicillin may cause allergic reactions that range from mild rashes to anaphylaxis. Unlike the more narrow-spectrum penicillin, they may cause antibiotic-associated diarrhea, including C difficile colitis,⁴ and they may eliminate part of the normal vaginal flora and stimulate an overgrowth of yeast organisms in the vagina. The cost of ampicillin and amoxicillin is very low. These 2 agents are used primarily for treatment of group A and B streptococci infections and some UTIs, particularly those caused by enterococci.^1,2

Dicloxacillin sodium

This penicillin derivative disrupts bacterial cell wall synthesis and targets primarily aerobic gram-positive cocci, particularly staphylococci species. The antibiotic is not active against MRSA. The principal adverse effects of dicloxacillin sodium are an allergic reaction and GI upset. The drug is very inexpensive.

The key application for dicloxacillin sodium in our specialty is for treatment of puerperal mastitis.¹

Continue to: Extended-spectrum penicillins...

Three interesting combination extended-spectrum penicillins are used widely in our specialty. They are ampicillin/sulbactam, amoxicillin/clavulanate, and piperacillin/tazobactam. Ampicillin/sulbactam may be administered intramuscularly and intravenously. Piperacillin/tazobactam is administered intravenously; amoxicillin/clavulanate is administered orally.

Clavulanate, sulbactam, and tazobactam are β-lactamase inhibitors. When added to the parent antibiotic (amoxicillin, ampicillin, and piperacillin, respectively), they significantly enhance the parent drug’s spectrum of activity. These agents interfere with bacterial cell wall synthesis. They provide excellent coverage of aerobic gram-positive cocci, including enterococci; anaerobic gram-positive cocci; anaerobic gram-negative bacilli; and aerobic gram-negative bacilli. Their principal adverse effects include allergic reactions and antibiotic-associated diarrhea. They are moderately expensive.

The principal application of ampicillin/sulbactam and piperacillin/tazobactam in our specialty is as single agents for treatment of puerperal endometritis, postoperative pelvic cellulitis, and pyelonephritis. The usual role for amoxicillin/clavulanate is for oral treatment of complicated UTIs, including pyelonephritis in early pregnancy, and for outpatient therapy of mild to moderately severe endometritis following delivery or pregnancy termination.

Macrolides, monobactams, and additional antibiotics

Azithromycin

Azithromycin is a macrolide antibiotic that is in the same class as erythromycin and clindamycin. In our specialty, it has largely replaced erythromycin because of its more convenient dosage schedule and its better tolerability. It inhibits bacterial protein synthesis, and it is available in both an oral and intravenous formulation.

Azithromycin has an excellent spectrum of activity against the 3 major microorganisms that cause otitis media, sinusitis, and bronchitis: Streptococcus pneumoniae, H influenzae, and M catarrhalis. It also provides excellent coverage of Chlamydia trachomatis, Mycoplasma pneumoniae, and genital mycoplasmas; in high doses it provides modest coverage against gonorrhea.⁸ Unlike erythromycin, it has minimal GI toxicity and is usually very well tolerated by most patients. One unusual, but very important, adverse effect of the drug is prolongation of the Q-T interval.⁹

Azithromycin is now available in generic form and is relatively inexpensive. As a single agent, its principal applications in our specialty are for treatment of respiratory tract infections such as otitis media, sinusitis, and acute bronchitis and for treatment of chlamydia urethritis and endocervicitis.^8,10 In combination with ampicillin, azithromycin is used as prophylaxis in patients with preterm premature rupture of membranes (PPROM), and, in combination with cefazolin, it is used for prophylaxis in patients undergoing cesarean delivery.^1,2,5

Aztreonam

Aztreonam is a monobactam antibiotic. Like the cephalosporins and penicillins, aztreonam inhibits bacterial cell wall synthesis. It may be administered intramuscularly and intravenously, and its principal spectrum of activity is against aerobic gram-negative bacilli, which is similar to the aminoglycosides’ spectrum.

Aztreonam’s most likely adverse effects include phlebitis at the injection site, allergy, GI upset, and diarrhea. The drug is moderately expensive. In our specialty, aztreonam could be used as a single agent, in lieu of an aminoglycoside, for treatment of pyelonephritis caused by an unusually resistant organism. It also could be used in combination with clindamycin or metronidazole plus ampicillin for treatment of polymicrobial infections, such as chorioamnionitis, puerperal endometritis, and pelvic cellulitis.^1,2

Continue to: Clindamycin...

Clindamycin

A macrolide antibiotic, clindamycin exerts its antibacterial effect by interfering with bacterial protein synthesis. It can be administered orally and intravenously. Its key spectrum of activity in our specialty includes GBS, staphylococci, and anaerobes. However, clindamycin is not active against enterococci or aerobic gram-negative bacilli. GI upset and antibiotic-induced diarrhea are its principal adverse effects, and clindamycin is one of the most important causes of C difficile colitis. Although it is available in a generic formulation, this drug is still relatively expensive.

Clindamycin’s principal application in our specialty is for treating staphylococcal infections, such as wound infections and mastitis. It is particularly effective against MRSA infections. When used in combination with an aminoglycoside such as gentamicin, clindamycin provides excellent treatment for chorioamnionitis, puerperal endometritis, and pelvic inflammatory disease. In fact, for many years, the combination of clindamycin plus gentamicin has been considered the gold standard for the treatment of polymicrobial, mixed aerobic-anaerobic pelvic infections.^1,2

Doxycycline

Doxycycline, a tetracycline, exerts its antibacterial effect by inhibiting bacterial protein synthesis. The drug targets a broad range of pelvic pathogens, including C trachomatis and N gonorrhoeae, and it may be administered both orally and intravenously. Doxycycline’s principal adverse effects include headache, GI upset, and photosensitivity. By disrupting the normal bowel and vaginal flora, the drug also can cause diarrhea and vulvovaginal moniliasis. In addition, it can cause permanent discoloration of the teeth, and, for this reason, doxycycline should not be used in pregnant or lactating women or in young children.

Although doxycycline has been available in generic formulation for many years, it remains relatively expensive. As a single agent, its principal application in our specialty is for treatment of chlamydia infection. It may be used as prophylaxis for surgical procedures, such as hysterectomy and pregnancy terminations. In combination with an extended-spectrum cephalosporin, it also may be used to treat pelvic inflammatory disease.^2,8,10

Metronidazole

Metronidazole, a nitroimidazole derivative, exerts its antibacterial effect by disrupting bacterial protein synthesis. The drug may be administered topically, orally, and intravenously. Its primary spectrum of activity is against anerobic microorganisms. It is also active against Giardia and Trichomonas vaginalis.

Metronidazole’s most common adverse effects are GI upset, a metallic taste in the mouth, and a disulfiram-like effect when taken with alcohol. The cost of oral and intravenous metronidazole is relatively low; ironically, the cost of topical metronidazole is relatively high. In our specialty, the principal applications of oral metronidazole are as a single agent for treatment of bacterial vaginosis and trichomoniasis. When combined with ampicillin plus an aminoglycoside, intravenous metronidazole provides excellent coverage against the diverse anaerobic microorganisms that cause chorioamnionitis, puerperal endometritis, and pelvic cellulitis.^1,2

Trimethoprim-sulfamethoxazole (TMP-SMX)

This antibiotic combination (an antifolate and a sulfonamide) inhibits sequential steps in the synthesis of folic acid, an essential nutrient in bacterial metabolism. It is available in both an intravenous and oral formulation. TMP-SMX has a broad spectrum of activity against the aerobic gram-negative bacilli that cause UTIs in women. In addition, it provides excellent coverage against staphylococci, including MRSA; Pneumocystis jirovecii; and Toxoplasma gondii.

The medication’s principal toxicity is an allergic reaction. Some reactions are quite severe, such as the Stevens-Johnson syndrome. TMP-SMX is relatively inexpensive, particularly the oral formulation. The most common indications for TMP-SMX in our specialty are for treatment of UTIs, mastitis, and wound infections.^1,2,11 In HIV-infected patients, the drug provides excellent prophylaxis against recurrent Pneumocystis and Toxoplasma infections. TMP-SMX should not be used in the first trimester of pregnancy because it has been linked to several birth defects, including neural tube defects, heart defects, choanal atresia, and diaphragmatic hernia.¹²

Nitrofurantoin

Usually administered orally as nitrofurantoin monohydrate macrocrystals, nitrofurantoin exerts its antibacterial effect primarily by inhibiting protein synthesis. Its principal spectrum of activity is against the aerobic gram-negative bacilli, with the exception of Proteus species. Nitrofurantoin’s most common adverse effects are GI upset, headache, vertigo, drowsiness, and allergic reactions. The drug is relatively inexpensive.

Nitrofurantoin is an excellent agent for the treatment of lower UTIs.¹¹ It is not well concentrated in the renal parenchyma or blood, however, so it should not be used to treat pyelonephritis. As a general rule, nitrofurantoin should not be used in the first trimester of pregnancy because it has been associated with eye, heart, and facial cleft defects in the fetus.¹²

Vancomycin

Vancomycin exerts its antibacterial effect by inhibiting cell wall synthesis. It may be administered both orally and intravenously, and it specifically targets aerobic gram-positive cocci, particularly methicillin-sensitive and methicillin-resistant staphylococci. Vancomycin’s most important adverse effects include GI upset, nephrotoxicity, ototoxicity, and severe allergic reactions, such as anaphylaxis, Stevens-Johnson syndrome, and exfoliative dermatitis (the “red man” syndrome). The drug is moderately expensive.¹³

In its oral formulation, vancomycin’s principal application in our discipline is for treating C difficile colitis. In its intravenous formulation, it is used primarily as a single agent for GBS prophylaxis in penicillin-allergic patients, and it is used in combination with other antibiotics, such as clindamycin plus gentamicin, for treating patients with deep-seated incisional (wound) infections.^1,2,13,14 ●

Gupta A, Jha P, Baran TM, et al. Ovarian cancer detection in average-risk women: classic- versus nonclassic-appearing adnexal lesions at US. Radiology. 2022;212338. doi: 10.1148/radiol.212338.

Expert commentary

Gupta and colleagues conducted a multicenter, retrospective review of 970 adnexal lesions among 878 women—75% were premenopausal and 25% were postmenopausal.

Imaging details

The lesions were characterized by pattern recognition as “classic” (simple cysts, endometriomas, hemorrhagic cysts, or dermoids) or “nonclassic.” Out of 673 classic lesions, there were 4 malignancies (0.6%), of which 1 was an endometrioma and 3 were classified as simple cysts. However, out of 297 nonclassic lesions (multilocular, unilocular with solid areas or wall irregularity, or mostly solid), 32% (33/103) were malignant when vascularity was present, while 8% (16/184) were malignant when no intralesional vascularity was appreciated.

The authors pointed out that, especially because their study was retrospective, there was no standardization of scan technique or equipment employed. However, this point adds credibility to the “real world” nature of such imaging.

Other data corroborate findings

Other studies have looked at pattern recognition in efforts to optimize a conservative approach to benign masses and referral to oncology for suspected malignant masses, as described above. This was the main cornerstone of the International Consensus Conference,² which also identified next steps for indeterminate masses, including evidence-based risk assessment algorithms and referral (to an expert imager or gynecologic oncologist). A multicenter trial in Europe³ found that ultrasound experience substantially impacts on diagnostic performance when adnexal masses are classified using pattern recognition. This occurred in a stepwise fashion with increasing accuracy directly related to the level of expertise. Shetty and colleagues⁴ found that pattern recognition performed better than the risk of malignancy index (sensitivities of 95% and 79%, respectively). ●

Gupta A, Jha P, Baran TM, et al. Ovarian cancer detection in average-risk women: classic- versus nonclassic-appearing adnexal lesions at US. Radiology. 2022;212338. doi: 10.1148/radiol.212338.

Expert commentary

Gupta and colleagues conducted a multicenter, retrospective review of 970 adnexal lesions among 878 women—75% were premenopausal and 25% were postmenopausal.

Imaging details

The lesions were characterized by pattern recognition as “classic” (simple cysts, endometriomas, hemorrhagic cysts, or dermoids) or “nonclassic.” Out of 673 classic lesions, there were 4 malignancies (0.6%), of which 1 was an endometrioma and 3 were classified as simple cysts. However, out of 297 nonclassic lesions (multilocular, unilocular with solid areas or wall irregularity, or mostly solid), 32% (33/103) were malignant when vascularity was present, while 8% (16/184) were malignant when no intralesional vascularity was appreciated.

The authors pointed out that, especially because their study was retrospective, there was no standardization of scan technique or equipment employed. However, this point adds credibility to the “real world” nature of such imaging.

Other data corroborate findings

Other studies have looked at pattern recognition in efforts to optimize a conservative approach to benign masses and referral to oncology for suspected malignant masses, as described above. This was the main cornerstone of the International Consensus Conference,² which also identified next steps for indeterminate masses, including evidence-based risk assessment algorithms and referral (to an expert imager or gynecologic oncologist). A multicenter trial in Europe³ found that ultrasound experience substantially impacts on diagnostic performance when adnexal masses are classified using pattern recognition. This occurred in a stepwise fashion with increasing accuracy directly related to the level of expertise. Shetty and colleagues⁴ found that pattern recognition performed better than the risk of malignancy index (sensitivities of 95% and 79%, respectively). ●

Gupta A, Jha P, Baran TM, et al. Ovarian cancer detection in average-risk women: classic- versus nonclassic-appearing adnexal lesions at US. Radiology. 2022;212338. doi: 10.1148/radiol.212338.

Expert commentary

Gupta and colleagues conducted a multicenter, retrospective review of 970 adnexal lesions among 878 women—75% were premenopausal and 25% were postmenopausal.

Imaging details

The lesions were characterized by pattern recognition as “classic” (simple cysts, endometriomas, hemorrhagic cysts, or dermoids) or “nonclassic.” Out of 673 classic lesions, there were 4 malignancies (0.6%), of which 1 was an endometrioma and 3 were classified as simple cysts. However, out of 297 nonclassic lesions (multilocular, unilocular with solid areas or wall irregularity, or mostly solid), 32% (33/103) were malignant when vascularity was present, while 8% (16/184) were malignant when no intralesional vascularity was appreciated.

The authors pointed out that, especially because their study was retrospective, there was no standardization of scan technique or equipment employed. However, this point adds credibility to the “real world” nature of such imaging.

Other data corroborate findings

Other studies have looked at pattern recognition in efforts to optimize a conservative approach to benign masses and referral to oncology for suspected malignant masses, as described above. This was the main cornerstone of the International Consensus Conference,² which also identified next steps for indeterminate masses, including evidence-based risk assessment algorithms and referral (to an expert imager or gynecologic oncologist). A multicenter trial in Europe³ found that ultrasound experience substantially impacts on diagnostic performance when adnexal masses are classified using pattern recognition. This occurred in a stepwise fashion with increasing accuracy directly related to the level of expertise. Shetty and colleagues⁴ found that pattern recognition performed better than the risk of malignancy index (sensitivities of 95% and 79%, respectively). ●

During pregnancy, anemia and iron deficiency are prevalent because the fetus depletes maternal iron stores. Iron deficiency and iron deficiency anemia are not synonymous. Effective screening for iron deficiency in the first trimester of pregnancy requires the measurement of a sensitive and specific biomarker of iron deficiency, such as ferritin. Limiting the measurement of ferritin to the subset of patients with anemia will result in missing many cases of iron deficiency. By the time iron deficiency causes anemia, a severe deficiency is present. Detecting iron deficiency in pregnancy and promptly treating the deficiency will reduce the number of women with anemia in the third trimester and at birth.

Diagnosis of anemia

Anemia in pregnancy is diagnosed by a hemoglobin level and hematocrit concentration below 11 g/dL and 33%, respectively, in the first and third trimesters and below 10.5 g/dL and 32%, respectively, in the second trimester.¹ The prevalence of anemia in the first, second, and third trimesters is approximately 3%, 2%, and 11%, respectively.² At a hemoglobin concentration <11 g/dL, severe maternal morbidity rises significantly.³ The laboratory evaluation of pregnant women with anemia may require assessment of iron stores, measurement of folate and cobalamin (vitamin B12), and hemoglobin electrophoresis, if indicated.

Diagnosis of iron deficiency

Iron deficiency anemia is diagnosed by a ferritin level below 30 ng/mL.^4,5 Normal iron stores and iron insufficiency are indicated by ferritin levels 45 to 150 ng/mL and 30 to 44 ng/mL, respectively.^4,5 Ferritin is an acute phase reactant, and patients with inflammation or chronic illnesses may have iron deficiency and a normal ferritin level. For these patients, a transferrin saturation (TSAT) <16% would support a diagnosis of iron deficiency.⁶ TSAT is calculated from measurement of serum iron and total iron binding capacity. TSAT saturation may be elevated by iron supplements, which increase serum iron. If measurement of TSAT is necessary, interference with the measurement accuracy can be minimized by not taking an iron supplement on the day of testing.

Iron deficiency is present in approximately 50% of pregnant women.^7,8 The greatest prevalence of iron deficiency in pregnancy is observed in non-Hispanic Black females, followed by Hispanic females. Non-Hispanic White females had the lowest prevalence of iron deficiency.²

Fetal needs for iron often cause the depletion of maternal iron stores. Many pregnant women who have a normal ferritin level in the first trimester will develop iron deficiency in the third trimester, even with the usual recommended daily oral iron supplementation. We recommend measuring ferritin and hemoglobin at the first prenatal visit and again between 24 and 28 weeks’ gestation.

Impact of maternal anemia on maternal and newborn health

Iron plays a critical role in maternal health and fetal development independent of its role in red blood cell formation. Many proteins critical to maternal health and fetal development contain iron, including hemoglobin, myoglobin, cytochromes, ribonucleotide reductase, peroxidases, lipoxygenases, and cyclooxygenases. In the fetus, iron plays an important role in myelination of nerves, dendrite arborization, and synthesis of monoamine neurotransmitters.⁹

Many studies report that maternal anemia is associated with severe maternal morbidity and adverse newborn outcomes. The current literature must be interpreted with caution because socioeconomic factors influence iron stores. Iron deficiency and anemia is more common among economically and socially disadvantaged populations.^10-12 It is possible that repleting iron stores, alone, without addressing social determinants of health, including food and housing insecurity, may be insufficient to improve maternal and newborn health.

Maternal anemia is a risk factor for severe maternal morbidity and adverse newborn outcomes.^3,13-18 In a study of 515,270 live births in British Columbia between 2004 and 2016, maternal anemia was diagnosed in 12.8% of mothers.¹⁵ Maternal morbidity at birth was increased among patients with mild anemia (hemoglobin concentration of 9 to 10.9 g/dL), including higher rates of intrapartum transfusion (adjusted odds ratio [OR], 2.45; 95% confidence interval [CI], 1.74-3.45), cesarean birth (aOR, 1.17; 95% CI, 1.14-1.19), and chorioamnionitis (aOR, 1.35; 95% CI, 1.27-1.44). Newborn morbidity was also increased among newborns of mothers with mild anemia (hemoglobin concentrations of 9 to 10.9 g/dL), including birth before 37 weeks’ gestation (aOR, 1.09; 95% CI, 1.05-1.12), birth before 32 weeks’ gestation (aOR, 1.30; 95% CI, 1.21-1.39), admission to the intensive care unit (aOR, 1.21; 95% CI, 1.17-1.25), and respiratory distress syndrome (aOR, 1.35; 95% CI, 1.24-1.46).¹⁵ Adverse maternal and newborn outcomes were more prevalent among mothers with moderate (hemoglobin concentrations of 7 to 8.9 g/dL) or severe anemia (hemoglobin concentrations of <7 g/dL), compared with mild anemia. For example, compared with mothers with no anemia, mothers with moderate anemia had an increased risk of birth <37 weeks (aOR, 2.26) and birth <32 weeks (aOR, 3.95).¹⁵

In a study of 166,566 US pregnant patients, 6.1% were diagnosed with anemia.¹⁸ Patients with anemia were more likely to have antepartum thrombosis, preeclampsia, eclampsia, a cesarean birth, postpartum hemorrhage, a blood transfusion, and postpartum thrombosis.¹⁸ In this study, the newborns of mothers with anemia were more likely to have a diagnosis of antenatal or intrapartum fetal distress, a 5-minute Apgar score <7, and an admission to the neonatal intensive care unit.

Continue to: Maternal anemia and neurodevelopmental disorders in children...

Some experts, but not all, believe that iron deficiency during pregnancy may adversely impact fetal neurodevelopment and result in childhood behavior issues. All experts agree that more research is needed to understand if maternal anemia causes mental health issues in newborns. In one meta-analysis, among 20 studies of the association of maternal iron deficiency and newborn neurodevelopment, approximately half the studies reported that low maternal ferritin levels were associated with lower childhood performance on standardized tests of cognitive, motor, verbal, and memory function.¹⁹ Another systematic review concluded that the evidence linking maternal iron deficiency and child neurodevelopment is equivocal.²⁰

In a study of 532,232 nonadoptive children born in Sweden from 1987 to 2010, maternal anemia was associated with an increased risk of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and intellectual disability (ID).²¹ In Sweden maternal hemoglobin concentration is measured at 10, 25, and 37 weeks of gestation, permitting comparisons of anemia diagnosed early and late in pregnancy with neurodevelopmental outcomes. The association between anemia and neurodevelopmental disorders was greatest if anemia was diagnosed within the first 30 weeks of pregnancy. Compared with mothers without anemia, maternal anemia diagnosed within the first 30 weeks of pregnancy was associated with higher childhood rates of ASD (4.9% vs 3.5%), ADHD (9.3% vs 7.1%), and ID (3.1% vs 1.3%).²¹ The differences persisted in analyses that controlled for socioeconomic, maternal, and pregnancy-related factors. In a matched sibling comparison, the diagnosis of maternal anemia within the first 30 weeks of gestation was associated with an increased risk of ASD (OR, 2.25; 95% CI, 1.24-4.11) and ID (OR, 2.59; 95% CI, 1.08-6.22) but not ADHD.²¹ Other studies have also reported a relationship between maternal anemia and intellectual disability.^22,23

Measurement of hemoglobin will identify anemia, but hemoglobin measurement is not sufficiently sensitive to identify most cases of iron deficiency. Measuring ferritin can help to identify cases of iron deficiency before the onset of anemia, permitting early treatment of the nutrient deficiency. In pregnancy, iron deficiency is the prelude to developing anemia. Waiting until anemia occurs to diagnose and treat iron deficiency is suboptimal and may miss a critical window of fetal development that is dependent on maternal iron stores. During pregnancy, ferritin levels decrease as much as 80% between the first and third trimesters, as the fetus utilizes maternal iron stores for its growth.²⁴ We recommend the measurement of ferritin and hemoglobin at the first prenatal visit and again at 24 to 28 weeks’ gestation to optimize early detection and treatment of iron deficiency and reduce the frequency of anemia prior to birth. ●

During pregnancy, anemia and iron deficiency are prevalent because the fetus depletes maternal iron stores. Iron deficiency and iron deficiency anemia are not synonymous. Effective screening for iron deficiency in the first trimester of pregnancy requires the measurement of a sensitive and specific biomarker of iron deficiency, such as ferritin. Limiting the measurement of ferritin to the subset of patients with anemia will result in missing many cases of iron deficiency. By the time iron deficiency causes anemia, a severe deficiency is present. Detecting iron deficiency in pregnancy and promptly treating the deficiency will reduce the number of women with anemia in the third trimester and at birth.

Diagnosis of anemia

Anemia in pregnancy is diagnosed by a hemoglobin level and hematocrit concentration below 11 g/dL and 33%, respectively, in the first and third trimesters and below 10.5 g/dL and 32%, respectively, in the second trimester.¹ The prevalence of anemia in the first, second, and third trimesters is approximately 3%, 2%, and 11%, respectively.² At a hemoglobin concentration <11 g/dL, severe maternal morbidity rises significantly.³ The laboratory evaluation of pregnant women with anemia may require assessment of iron stores, measurement of folate and cobalamin (vitamin B12), and hemoglobin electrophoresis, if indicated.

Diagnosis of iron deficiency

Iron deficiency anemia is diagnosed by a ferritin level below 30 ng/mL.^4,5 Normal iron stores and iron insufficiency are indicated by ferritin levels 45 to 150 ng/mL and 30 to 44 ng/mL, respectively.^4,5 Ferritin is an acute phase reactant, and patients with inflammation or chronic illnesses may have iron deficiency and a normal ferritin level. For these patients, a transferrin saturation (TSAT) <16% would support a diagnosis of iron deficiency.⁶ TSAT is calculated from measurement of serum iron and total iron binding capacity. TSAT saturation may be elevated by iron supplements, which increase serum iron. If measurement of TSAT is necessary, interference with the measurement accuracy can be minimized by not taking an iron supplement on the day of testing.

Iron deficiency is present in approximately 50% of pregnant women.^7,8 The greatest prevalence of iron deficiency in pregnancy is observed in non-Hispanic Black females, followed by Hispanic females. Non-Hispanic White females had the lowest prevalence of iron deficiency.²

Fetal needs for iron often cause the depletion of maternal iron stores. Many pregnant women who have a normal ferritin level in the first trimester will develop iron deficiency in the third trimester, even with the usual recommended daily oral iron supplementation. We recommend measuring ferritin and hemoglobin at the first prenatal visit and again between 24 and 28 weeks’ gestation.

Impact of maternal anemia on maternal and newborn health

Iron plays a critical role in maternal health and fetal development independent of its role in red blood cell formation. Many proteins critical to maternal health and fetal development contain iron, including hemoglobin, myoglobin, cytochromes, ribonucleotide reductase, peroxidases, lipoxygenases, and cyclooxygenases. In the fetus, iron plays an important role in myelination of nerves, dendrite arborization, and synthesis of monoamine neurotransmitters.⁹

Many studies report that maternal anemia is associated with severe maternal morbidity and adverse newborn outcomes. The current literature must be interpreted with caution because socioeconomic factors influence iron stores. Iron deficiency and anemia is more common among economically and socially disadvantaged populations.^10-12 It is possible that repleting iron stores, alone, without addressing social determinants of health, including food and housing insecurity, may be insufficient to improve maternal and newborn health.

Maternal anemia is a risk factor for severe maternal morbidity and adverse newborn outcomes.^3,13-18 In a study of 515,270 live births in British Columbia between 2004 and 2016, maternal anemia was diagnosed in 12.8% of mothers.¹⁵ Maternal morbidity at birth was increased among patients with mild anemia (hemoglobin concentration of 9 to 10.9 g/dL), including higher rates of intrapartum transfusion (adjusted odds ratio [OR], 2.45; 95% confidence interval [CI], 1.74-3.45), cesarean birth (aOR, 1.17; 95% CI, 1.14-1.19), and chorioamnionitis (aOR, 1.35; 95% CI, 1.27-1.44). Newborn morbidity was also increased among newborns of mothers with mild anemia (hemoglobin concentrations of 9 to 10.9 g/dL), including birth before 37 weeks’ gestation (aOR, 1.09; 95% CI, 1.05-1.12), birth before 32 weeks’ gestation (aOR, 1.30; 95% CI, 1.21-1.39), admission to the intensive care unit (aOR, 1.21; 95% CI, 1.17-1.25), and respiratory distress syndrome (aOR, 1.35; 95% CI, 1.24-1.46).¹⁵ Adverse maternal and newborn outcomes were more prevalent among mothers with moderate (hemoglobin concentrations of 7 to 8.9 g/dL) or severe anemia (hemoglobin concentrations of <7 g/dL), compared with mild anemia. For example, compared with mothers with no anemia, mothers with moderate anemia had an increased risk of birth <37 weeks (aOR, 2.26) and birth <32 weeks (aOR, 3.95).¹⁵

In a study of 166,566 US pregnant patients, 6.1% were diagnosed with anemia.¹⁸ Patients with anemia were more likely to have antepartum thrombosis, preeclampsia, eclampsia, a cesarean birth, postpartum hemorrhage, a blood transfusion, and postpartum thrombosis.¹⁸ In this study, the newborns of mothers with anemia were more likely to have a diagnosis of antenatal or intrapartum fetal distress, a 5-minute Apgar score <7, and an admission to the neonatal intensive care unit.

Continue to: Maternal anemia and neurodevelopmental disorders in children...

Some experts, but not all, believe that iron deficiency during pregnancy may adversely impact fetal neurodevelopment and result in childhood behavior issues. All experts agree that more research is needed to understand if maternal anemia causes mental health issues in newborns. In one meta-analysis, among 20 studies of the association of maternal iron deficiency and newborn neurodevelopment, approximately half the studies reported that low maternal ferritin levels were associated with lower childhood performance on standardized tests of cognitive, motor, verbal, and memory function.¹⁹ Another systematic review concluded that the evidence linking maternal iron deficiency and child neurodevelopment is equivocal.²⁰

In a study of 532,232 nonadoptive children born in Sweden from 1987 to 2010, maternal anemia was associated with an increased risk of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and intellectual disability (ID).²¹ In Sweden maternal hemoglobin concentration is measured at 10, 25, and 37 weeks of gestation, permitting comparisons of anemia diagnosed early and late in pregnancy with neurodevelopmental outcomes. The association between anemia and neurodevelopmental disorders was greatest if anemia was diagnosed within the first 30 weeks of pregnancy. Compared with mothers without anemia, maternal anemia diagnosed within the first 30 weeks of pregnancy was associated with higher childhood rates of ASD (4.9% vs 3.5%), ADHD (9.3% vs 7.1%), and ID (3.1% vs 1.3%).²¹ The differences persisted in analyses that controlled for socioeconomic, maternal, and pregnancy-related factors. In a matched sibling comparison, the diagnosis of maternal anemia within the first 30 weeks of gestation was associated with an increased risk of ASD (OR, 2.25; 95% CI, 1.24-4.11) and ID (OR, 2.59; 95% CI, 1.08-6.22) but not ADHD.²¹ Other studies have also reported a relationship between maternal anemia and intellectual disability.^22,23

Measurement of hemoglobin will identify anemia, but hemoglobin measurement is not sufficiently sensitive to identify most cases of iron deficiency. Measuring ferritin can help to identify cases of iron deficiency before the onset of anemia, permitting early treatment of the nutrient deficiency. In pregnancy, iron deficiency is the prelude to developing anemia. Waiting until anemia occurs to diagnose and treat iron deficiency is suboptimal and may miss a critical window of fetal development that is dependent on maternal iron stores. During pregnancy, ferritin levels decrease as much as 80% between the first and third trimesters, as the fetus utilizes maternal iron stores for its growth.²⁴ We recommend the measurement of ferritin and hemoglobin at the first prenatal visit and again at 24 to 28 weeks’ gestation to optimize early detection and treatment of iron deficiency and reduce the frequency of anemia prior to birth. ●

During pregnancy, anemia and iron deficiency are prevalent because the fetus depletes maternal iron stores. Iron deficiency and iron deficiency anemia are not synonymous. Effective screening for iron deficiency in the first trimester of pregnancy requires the measurement of a sensitive and specific biomarker of iron deficiency, such as ferritin. Limiting the measurement of ferritin to the subset of patients with anemia will result in missing many cases of iron deficiency. By the time iron deficiency causes anemia, a severe deficiency is present. Detecting iron deficiency in pregnancy and promptly treating the deficiency will reduce the number of women with anemia in the third trimester and at birth.

Diagnosis of anemia

Anemia in pregnancy is diagnosed by a hemoglobin level and hematocrit concentration below 11 g/dL and 33%, respectively, in the first and third trimesters and below 10.5 g/dL and 32%, respectively, in the second trimester.¹ The prevalence of anemia in the first, second, and third trimesters is approximately 3%, 2%, and 11%, respectively.² At a hemoglobin concentration <11 g/dL, severe maternal morbidity rises significantly.³ The laboratory evaluation of pregnant women with anemia may require assessment of iron stores, measurement of folate and cobalamin (vitamin B12), and hemoglobin electrophoresis, if indicated.

Diagnosis of iron deficiency

Iron deficiency anemia is diagnosed by a ferritin level below 30 ng/mL.^4,5 Normal iron stores and iron insufficiency are indicated by ferritin levels 45 to 150 ng/mL and 30 to 44 ng/mL, respectively.^4,5 Ferritin is an acute phase reactant, and patients with inflammation or chronic illnesses may have iron deficiency and a normal ferritin level. For these patients, a transferrin saturation (TSAT) <16% would support a diagnosis of iron deficiency.⁶ TSAT is calculated from measurement of serum iron and total iron binding capacity. TSAT saturation may be elevated by iron supplements, which increase serum iron. If measurement of TSAT is necessary, interference with the measurement accuracy can be minimized by not taking an iron supplement on the day of testing.

Iron deficiency is present in approximately 50% of pregnant women.^7,8 The greatest prevalence of iron deficiency in pregnancy is observed in non-Hispanic Black females, followed by Hispanic females. Non-Hispanic White females had the lowest prevalence of iron deficiency.²

Fetal needs for iron often cause the depletion of maternal iron stores. Many pregnant women who have a normal ferritin level in the first trimester will develop iron deficiency in the third trimester, even with the usual recommended daily oral iron supplementation. We recommend measuring ferritin and hemoglobin at the first prenatal visit and again between 24 and 28 weeks’ gestation.

Impact of maternal anemia on maternal and newborn health

Iron plays a critical role in maternal health and fetal development independent of its role in red blood cell formation. Many proteins critical to maternal health and fetal development contain iron, including hemoglobin, myoglobin, cytochromes, ribonucleotide reductase, peroxidases, lipoxygenases, and cyclooxygenases. In the fetus, iron plays an important role in myelination of nerves, dendrite arborization, and synthesis of monoamine neurotransmitters.⁹

Many studies report that maternal anemia is associated with severe maternal morbidity and adverse newborn outcomes. The current literature must be interpreted with caution because socioeconomic factors influence iron stores. Iron deficiency and anemia is more common among economically and socially disadvantaged populations.^10-12 It is possible that repleting iron stores, alone, without addressing social determinants of health, including food and housing insecurity, may be insufficient to improve maternal and newborn health.

Maternal anemia is a risk factor for severe maternal morbidity and adverse newborn outcomes.^3,13-18 In a study of 515,270 live births in British Columbia between 2004 and 2016, maternal anemia was diagnosed in 12.8% of mothers.¹⁵ Maternal morbidity at birth was increased among patients with mild anemia (hemoglobin concentration of 9 to 10.9 g/dL), including higher rates of intrapartum transfusion (adjusted odds ratio [OR], 2.45; 95% confidence interval [CI], 1.74-3.45), cesarean birth (aOR, 1.17; 95% CI, 1.14-1.19), and chorioamnionitis (aOR, 1.35; 95% CI, 1.27-1.44). Newborn morbidity was also increased among newborns of mothers with mild anemia (hemoglobin concentrations of 9 to 10.9 g/dL), including birth before 37 weeks’ gestation (aOR, 1.09; 95% CI, 1.05-1.12), birth before 32 weeks’ gestation (aOR, 1.30; 95% CI, 1.21-1.39), admission to the intensive care unit (aOR, 1.21; 95% CI, 1.17-1.25), and respiratory distress syndrome (aOR, 1.35; 95% CI, 1.24-1.46).¹⁵ Adverse maternal and newborn outcomes were more prevalent among mothers with moderate (hemoglobin concentrations of 7 to 8.9 g/dL) or severe anemia (hemoglobin concentrations of <7 g/dL), compared with mild anemia. For example, compared with mothers with no anemia, mothers with moderate anemia had an increased risk of birth <37 weeks (aOR, 2.26) and birth <32 weeks (aOR, 3.95).¹⁵

In a study of 166,566 US pregnant patients, 6.1% were diagnosed with anemia.¹⁸ Patients with anemia were more likely to have antepartum thrombosis, preeclampsia, eclampsia, a cesarean birth, postpartum hemorrhage, a blood transfusion, and postpartum thrombosis.¹⁸ In this study, the newborns of mothers with anemia were more likely to have a diagnosis of antenatal or intrapartum fetal distress, a 5-minute Apgar score <7, and an admission to the neonatal intensive care unit.

Continue to: Maternal anemia and neurodevelopmental disorders in children...

Some experts, but not all, believe that iron deficiency during pregnancy may adversely impact fetal neurodevelopment and result in childhood behavior issues. All experts agree that more research is needed to understand if maternal anemia causes mental health issues in newborns. In one meta-analysis, among 20 studies of the association of maternal iron deficiency and newborn neurodevelopment, approximately half the studies reported that low maternal ferritin levels were associated with lower childhood performance on standardized tests of cognitive, motor, verbal, and memory function.¹⁹ Another systematic review concluded that the evidence linking maternal iron deficiency and child neurodevelopment is equivocal.²⁰

In a study of 532,232 nonadoptive children born in Sweden from 1987 to 2010, maternal anemia was associated with an increased risk of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and intellectual disability (ID).²¹ In Sweden maternal hemoglobin concentration is measured at 10, 25, and 37 weeks of gestation, permitting comparisons of anemia diagnosed early and late in pregnancy with neurodevelopmental outcomes. The association between anemia and neurodevelopmental disorders was greatest if anemia was diagnosed within the first 30 weeks of pregnancy. Compared with mothers without anemia, maternal anemia diagnosed within the first 30 weeks of pregnancy was associated with higher childhood rates of ASD (4.9% vs 3.5%), ADHD (9.3% vs 7.1%), and ID (3.1% vs 1.3%).²¹ The differences persisted in analyses that controlled for socioeconomic, maternal, and pregnancy-related factors. In a matched sibling comparison, the diagnosis of maternal anemia within the first 30 weeks of gestation was associated with an increased risk of ASD (OR, 2.25; 95% CI, 1.24-4.11) and ID (OR, 2.59; 95% CI, 1.08-6.22) but not ADHD.²¹ Other studies have also reported a relationship between maternal anemia and intellectual disability.^22,23

Measurement of hemoglobin will identify anemia, but hemoglobin measurement is not sufficiently sensitive to identify most cases of iron deficiency. Measuring ferritin can help to identify cases of iron deficiency before the onset of anemia, permitting early treatment of the nutrient deficiency. In pregnancy, iron deficiency is the prelude to developing anemia. Waiting until anemia occurs to diagnose and treat iron deficiency is suboptimal and may miss a critical window of fetal development that is dependent on maternal iron stores. During pregnancy, ferritin levels decrease as much as 80% between the first and third trimesters, as the fetus utilizes maternal iron stores for its growth.²⁴ We recommend the measurement of ferritin and hemoglobin at the first prenatal visit and again at 24 to 28 weeks’ gestation to optimize early detection and treatment of iron deficiency and reduce the frequency of anemia prior to birth. ●

Muraca GM, Boutin A, Razaz N, et al. Maternal and neonatal trauma following operative vaginal delivery. CMAJ. 2022;194:E1-E12. doi: 10.1503/cmaj.210841.
 

EXPERT COMMENTARY 

Operative vaginal delivery is used to achieve and expedite safe vaginal birth while avoiding CD and its associated morbidities.^1,2 Despite support from the American College of Obstetricians and Gynecologists (ACOG) for the use of OVD as an alternative to CD, OVD was used in only 3% of all US births in 2013, a shift from approximately 30% in 1987.^1,3 Reported complications of OVD are biased by the level of experience of the operator, changes in practice, and by misinterpretation of the counterfactual.¹

Outcomes of OVD should be compared with appropriate reference groups, namely, with second-stage CD births rather than with spontaneous vaginal births.⁴ With decreasing rates of OVD, evidence of contemporary data is needed on appropriately compared perinatal outcomes.⁴
 

Details of the study 

Muraca and colleagues conducted an observational cohort study of births in Canada between 2013 and 2019 to assess the incidence of maternal and neonatal trauma following OVD. They used composites defined a priori— stratified by instrument, region, level of obstetric care, and institutional OVD volume. 

Results. Among 1,326,191 live or stillbirths, 2.9% were attempted forceps deliveries and 8.4% were attempted vacuum deliveries. Following forceps delivery, the maternal trauma rate was 25.3% (95% confidence interval [CI], 24.8%–25.7%), and the neonatal trauma rate was 9.6 per 1,000 live births (95% CI, 8.6–10.6). Following vacuum delivery, maternal and neonatal trauma rates were 13.2% (95% CI, 13.0%–13.4%) and 9.6 per 1,000 live births (95% CI, 9.0–10.2), respectively. Maternal trauma was driven by higher order perineal lacerations. Some association was seen between increased forceps volume and decreased maternal trauma rates. 

The authors concluded that in Canada, rates of maternal and neonatal trauma following OVD are higher than previously reported in consensus statements.

Study strengths and limitations

This large contemporary study uniquely stratified perinatal outcomes following OVD. The outcomes are well defined and meaningful, but some limitations affect the generalizability of the findings. 

First, stillbirths were included for the maternal composite outcome, yet the incidence of this within the study population is not reported. Operative vaginal deliveries that involve stillbirths can be complex; a subgroup analysis excluding these would aid in interpretation.

Second, complicated OVDs, including sequential use of forceps and vacuum and OVDs from midpelvic station, were included; ACOG recommends against both these practices in routine circumstances due to known increases in maternal and neonatal morbidity.¹ As such, the inclusion of these OVDs may bias results away from the null. 

Finally, despite discussing the role of episiotomy, the episiotomy rate in this cohort is not reported.

Despite these limitations, the study by Muraca and colleagues is a positive step forward toward understanding the role of OVD in contemporary obstetric practice, and it uniquely ascertains the impact of OVD volume outcomes that previously had been an elusive exposure ●
 

Muraca GM, Boutin A, Razaz N, et al. Maternal and neonatal trauma following operative vaginal delivery. CMAJ. 2022;194:E1-E12. doi: 10.1503/cmaj.210841.
 

EXPERT COMMENTARY 

Operative vaginal delivery is used to achieve and expedite safe vaginal birth while avoiding CD and its associated morbidities.^1,2 Despite support from the American College of Obstetricians and Gynecologists (ACOG) for the use of OVD as an alternative to CD, OVD was used in only 3% of all US births in 2013, a shift from approximately 30% in 1987.^1,3 Reported complications of OVD are biased by the level of experience of the operator, changes in practice, and by misinterpretation of the counterfactual.¹

Outcomes of OVD should be compared with appropriate reference groups, namely, with second-stage CD births rather than with spontaneous vaginal births.⁴ With decreasing rates of OVD, evidence of contemporary data is needed on appropriately compared perinatal outcomes.⁴
 

Details of the study 

Muraca and colleagues conducted an observational cohort study of births in Canada between 2013 and 2019 to assess the incidence of maternal and neonatal trauma following OVD. They used composites defined a priori— stratified by instrument, region, level of obstetric care, and institutional OVD volume. 

Results. Among 1,326,191 live or stillbirths, 2.9% were attempted forceps deliveries and 8.4% were attempted vacuum deliveries. Following forceps delivery, the maternal trauma rate was 25.3% (95% confidence interval [CI], 24.8%–25.7%), and the neonatal trauma rate was 9.6 per 1,000 live births (95% CI, 8.6–10.6). Following vacuum delivery, maternal and neonatal trauma rates were 13.2% (95% CI, 13.0%–13.4%) and 9.6 per 1,000 live births (95% CI, 9.0–10.2), respectively. Maternal trauma was driven by higher order perineal lacerations. Some association was seen between increased forceps volume and decreased maternal trauma rates. 

The authors concluded that in Canada, rates of maternal and neonatal trauma following OVD are higher than previously reported in consensus statements.

Study strengths and limitations

This large contemporary study uniquely stratified perinatal outcomes following OVD. The outcomes are well defined and meaningful, but some limitations affect the generalizability of the findings. 

First, stillbirths were included for the maternal composite outcome, yet the incidence of this within the study population is not reported. Operative vaginal deliveries that involve stillbirths can be complex; a subgroup analysis excluding these would aid in interpretation.

Second, complicated OVDs, including sequential use of forceps and vacuum and OVDs from midpelvic station, were included; ACOG recommends against both these practices in routine circumstances due to known increases in maternal and neonatal morbidity.¹ As such, the inclusion of these OVDs may bias results away from the null. 

Finally, despite discussing the role of episiotomy, the episiotomy rate in this cohort is not reported.

Despite these limitations, the study by Muraca and colleagues is a positive step forward toward understanding the role of OVD in contemporary obstetric practice, and it uniquely ascertains the impact of OVD volume outcomes that previously had been an elusive exposure ●
 

Muraca GM, Boutin A, Razaz N, et al. Maternal and neonatal trauma following operative vaginal delivery. CMAJ. 2022;194:E1-E12. doi: 10.1503/cmaj.210841.
 

EXPERT COMMENTARY 

Operative vaginal delivery is used to achieve and expedite safe vaginal birth while avoiding CD and its associated morbidities.^1,2 Despite support from the American College of Obstetricians and Gynecologists (ACOG) for the use of OVD as an alternative to CD, OVD was used in only 3% of all US births in 2013, a shift from approximately 30% in 1987.^1,3 Reported complications of OVD are biased by the level of experience of the operator, changes in practice, and by misinterpretation of the counterfactual.¹

Outcomes of OVD should be compared with appropriate reference groups, namely, with second-stage CD births rather than with spontaneous vaginal births.⁴ With decreasing rates of OVD, evidence of contemporary data is needed on appropriately compared perinatal outcomes.⁴
 

Details of the study 

Muraca and colleagues conducted an observational cohort study of births in Canada between 2013 and 2019 to assess the incidence of maternal and neonatal trauma following OVD. They used composites defined a priori— stratified by instrument, region, level of obstetric care, and institutional OVD volume. 

Results. Among 1,326,191 live or stillbirths, 2.9% were attempted forceps deliveries and 8.4% were attempted vacuum deliveries. Following forceps delivery, the maternal trauma rate was 25.3% (95% confidence interval [CI], 24.8%–25.7%), and the neonatal trauma rate was 9.6 per 1,000 live births (95% CI, 8.6–10.6). Following vacuum delivery, maternal and neonatal trauma rates were 13.2% (95% CI, 13.0%–13.4%) and 9.6 per 1,000 live births (95% CI, 9.0–10.2), respectively. Maternal trauma was driven by higher order perineal lacerations. Some association was seen between increased forceps volume and decreased maternal trauma rates. 

The authors concluded that in Canada, rates of maternal and neonatal trauma following OVD are higher than previously reported in consensus statements.

Study strengths and limitations

This large contemporary study uniquely stratified perinatal outcomes following OVD. The outcomes are well defined and meaningful, but some limitations affect the generalizability of the findings. 

First, stillbirths were included for the maternal composite outcome, yet the incidence of this within the study population is not reported. Operative vaginal deliveries that involve stillbirths can be complex; a subgroup analysis excluding these would aid in interpretation.

Second, complicated OVDs, including sequential use of forceps and vacuum and OVDs from midpelvic station, were included; ACOG recommends against both these practices in routine circumstances due to known increases in maternal and neonatal morbidity.¹ As such, the inclusion of these OVDs may bias results away from the null. 

Finally, despite discussing the role of episiotomy, the episiotomy rate in this cohort is not reported.

Despite these limitations, the study by Muraca and colleagues is a positive step forward toward understanding the role of OVD in contemporary obstetric practice, and it uniquely ascertains the impact of OVD volume outcomes that previously had been an elusive exposure ●
 

What are the 2 most likely causes for persistent fever in a patient who is being treated with antibiotics for postcesarean endometritis?

Continue to the answer...

The 2 most likely causes of a poor response to treatment for postcesarean endometritis are a resistant microorganism and wound infection. Less common causes of persistent postoperative fever include septic pelvic vein thrombophlebitis, pelvic abscess, retained products of conception, reactivation of a connective tissue disorder, and drug fever.

What are the 2 most likely causes for persistent fever in a patient who is being treated with antibiotics for postcesarean endometritis?

Continue to the answer...

The 2 most likely causes of a poor response to treatment for postcesarean endometritis are a resistant microorganism and wound infection. Less common causes of persistent postoperative fever include septic pelvic vein thrombophlebitis, pelvic abscess, retained products of conception, reactivation of a connective tissue disorder, and drug fever.

What are the 2 most likely causes for persistent fever in a patient who is being treated with antibiotics for postcesarean endometritis?

Continue to the answer...

The 2 most likely causes of a poor response to treatment for postcesarean endometritis are a resistant microorganism and wound infection. Less common causes of persistent postoperative fever include septic pelvic vein thrombophlebitis, pelvic abscess, retained products of conception, reactivation of a connective tissue disorder, and drug fever.

_{Text copyright DenseBreast-info.org.}

Answer

B.  The Gail risk model^1-3 is used to predict 5-year and lifetime risks of developing invasive breast cancer, and to identify women who may benefit from risk-reducing medications such as tamoxifen. The Gail model should not be used to determine risk for purposes of screening magnetic resonance imaging (MRI)⁴ (or genetic testing).

Breast cancer risk models are used to stratify patients into risk categories to facilitate personalized screening and surveillance plans for clinical management. Several breast cancer risk assessment tools have been developed that include different combinations of known risk factors and are used for the following purposes: 

1. To identify women who may benefit from risk-reducing medications. The Gail model is used to determine risk for purposes of advising on use of risk-reducing medications. Any woman with a 5-year risk ≥1.67% by the Gail model may be considered for treatment with tamoxifen (pre or postmenopausal), raloxifene (postmenopausal), or aromatase inhibitors (postmenopausal).⁵  

In the National Surgical Adjuvant Breast and Bowel Project (NSABP) P1 study,⁶ women at increased risk for breast cancer were defined as follows: 

• age 35 to 59 years with at least a 1.66% 5-year risk for developing breast cancer by the Gail model
• personal history of lobular carcinoma in situ (LCIS)
• age over 60 years.

More than 13,000 such women were randomly assigned to receive tamoxifen or placebo daily for 5 years. Tamoxifen reduced the risk of invasive breast cancer by 49% and reduced the risk of noninvasive cancer by 50% compared with placebo. The reduced risk of breast cancer was only seen for estrogen-receptor–expressing tumors. There was a 2.5-fold increase in risk of endometrial cancer in women taking tamoxifen and a decrease in hip and spine fracture risk. Blood clots causing stroke and deep vein thrombosis are increased in women taking tamoxifen.^7,8

2. To identify women who may carry a pathogenic mutation in BRCA1 or BRCA2. Some models (eg, Tyrer-Cuzick [IBIS],⁹ Penn II,¹⁰ BOADICEA,¹¹ and BRCAPRO¹²) estimate the probability of a BRCA1/2 mutation; however, most testing guidelines are now criterion based (eg, National Comprehensive Cancer Network [NCCN]) as opposed to probability based. In practical terms, clinical decision making around genetic testing is rarely based on a priori probabilities. 

3.  To identify women who meet criteria for high-risk screening MRI. Current American Cancer Society (ACS) guidelines⁴ recommend annual screening MRI, in addition to mammography, beginning by age 25 to 30 in women who have a lifetime risk of breast cancer ≥20%. Any of the models used to predict risk of a pathogenic mutation (Tyrer-Cuzick [IBIS], Penn II, BOADICEA, BRCAPRO),or the Claus model,¹³ but not the Gail model, can be used to estimate lifetime risk for purposes of screening MRI guidelines. The ACS and NCCN guidelines specifically recommend against using the Gail model to determine risk for purposes of MRI screening or risk of pathogenic mutation, as it does not include detailed family history such as age at diagnosis or second-degree relatives. 

ACS and NCCN guidelines also recommend annual screening MRI beginning by age 25, with the addition of mammography beginning at age 30, in women who are known to carry pathogenic mutations in BRCA1 or BRCA2 (unless the woman has had bilateral mastectomy), and in women who are first-degree relatives of known mutation carriers but who are themselves untested.¹⁴ 

Women who are known to carry or are first-degree untested relatives of individuals with less common disease-causing mutations (such as those associated with Li-Fraumeni syndrome, Bannayan-Riley-Ruvalcaba syndrome, hereditary diffuse gastric cancer, Peutz-Jeghers syndrome, Cowden syndrome, Neurofibromatosis type 1, or Fanconi anemia) are also recommended for annual screening MRI beginning between ages 20-35, depending on the mutation.¹⁴ Women with known pathogenic mutations in ATM, CHEK2, or NBN should consider annual MRI starting at age 40 or 5-10 years before the earliest known breast cancer in the family (whichever comes first). 

Finally, women with prior chest radiation therapy (such as for Hodgkin disease) between ages 10 and 30 are at high risk for developing breast cancer,^4,15,16 with risk similar in magnitude to pathogenic BRCA1 or BRCA2  carriers. These women are also recommended for annual screening MRI starting at age 25 or 8 years after the chest radiation therapy, whichever is later.

Currently the Tyrer-Cuzick Model (IBIS) version 817 and the Breast Cancer Surveillance Consortium (BCSC) models¹⁸ include breast density in risk calculations; the Gail, Penn II, and Claus models do not include breast density. 

Adding polygenic risk scores based on single nucleotide polymorphisms to traditional comprehensive risk models such as the Tyrer-Cuzick model has been shown to improve model performance.¹⁹ In addition, artificial intelligence is being used to identify textural and other findings beyond breast density on mammograms that predict increased risk. Such information, which is complementary to the Tyrer-Cuzick model (v.8),²⁰ has more accurately identified high-risk patients than the Tyrer-Cuzick v8 risk model and prior deep learning models.²¹ 

In a study from the Karolinska Institute, a model that included computer-aided detection of microcalcifications and masses in addition to other traditional risk factors (including breast density) successfully identified women who would develop interval or advanced cancer in the 2 years after a normal mammogram and improved short-term (2-to-3-year) risk assessment over TyrerCuzick (v.7) or Gail models.²² This model proved more accurate than traditional risk models and can augment genetic/family history to help identify women who should and, importantly, who should not, have supplemental screening after 2D mammography. Risk models that include detailed family history should be used rather than the Gail model to identify women who meet high risk criteria for MRI screening. Research also supports the benefits of MRI in women with dense breasts who are not otherwise considered “high risk,” and while not widely available, lower cost, abbreviated MRI protocols have been validated for all women with dense breasts.²³ For more details on risk models, including a risk models table with live links to commonly used breast cancer risk assessment tools, visit https://densebreast-info .org/for-providers/risk-model-tutorial/. ●

_{Text copyright DenseBreast-info.org.}

Answer

B.  The Gail risk model^1-3 is used to predict 5-year and lifetime risks of developing invasive breast cancer, and to identify women who may benefit from risk-reducing medications such as tamoxifen. The Gail model should not be used to determine risk for purposes of screening magnetic resonance imaging (MRI)⁴ (or genetic testing).

Breast cancer risk models are used to stratify patients into risk categories to facilitate personalized screening and surveillance plans for clinical management. Several breast cancer risk assessment tools have been developed that include different combinations of known risk factors and are used for the following purposes: 

1. To identify women who may benefit from risk-reducing medications. The Gail model is used to determine risk for purposes of advising on use of risk-reducing medications. Any woman with a 5-year risk ≥1.67% by the Gail model may be considered for treatment with tamoxifen (pre or postmenopausal), raloxifene (postmenopausal), or aromatase inhibitors (postmenopausal).⁵  

In the National Surgical Adjuvant Breast and Bowel Project (NSABP) P1 study,⁶ women at increased risk for breast cancer were defined as follows: 

• age 35 to 59 years with at least a 1.66% 5-year risk for developing breast cancer by the Gail model
• personal history of lobular carcinoma in situ (LCIS)
• age over 60 years.

More than 13,000 such women were randomly assigned to receive tamoxifen or placebo daily for 5 years. Tamoxifen reduced the risk of invasive breast cancer by 49% and reduced the risk of noninvasive cancer by 50% compared with placebo. The reduced risk of breast cancer was only seen for estrogen-receptor–expressing tumors. There was a 2.5-fold increase in risk of endometrial cancer in women taking tamoxifen and a decrease in hip and spine fracture risk. Blood clots causing stroke and deep vein thrombosis are increased in women taking tamoxifen.^7,8

2. To identify women who may carry a pathogenic mutation in BRCA1 or BRCA2. Some models (eg, Tyrer-Cuzick [IBIS],⁹ Penn II,¹⁰ BOADICEA,¹¹ and BRCAPRO¹²) estimate the probability of a BRCA1/2 mutation; however, most testing guidelines are now criterion based (eg, National Comprehensive Cancer Network [NCCN]) as opposed to probability based. In practical terms, clinical decision making around genetic testing is rarely based on a priori probabilities. 

3.  To identify women who meet criteria for high-risk screening MRI. Current American Cancer Society (ACS) guidelines⁴ recommend annual screening MRI, in addition to mammography, beginning by age 25 to 30 in women who have a lifetime risk of breast cancer ≥20%. Any of the models used to predict risk of a pathogenic mutation (Tyrer-Cuzick [IBIS], Penn II, BOADICEA, BRCAPRO),or the Claus model,¹³ but not the Gail model, can be used to estimate lifetime risk for purposes of screening MRI guidelines. The ACS and NCCN guidelines specifically recommend against using the Gail model to determine risk for purposes of MRI screening or risk of pathogenic mutation, as it does not include detailed family history such as age at diagnosis or second-degree relatives. 

ACS and NCCN guidelines also recommend annual screening MRI beginning by age 25, with the addition of mammography beginning at age 30, in women who are known to carry pathogenic mutations in BRCA1 or BRCA2 (unless the woman has had bilateral mastectomy), and in women who are first-degree relatives of known mutation carriers but who are themselves untested.¹⁴ 

Women who are known to carry or are first-degree untested relatives of individuals with less common disease-causing mutations (such as those associated with Li-Fraumeni syndrome, Bannayan-Riley-Ruvalcaba syndrome, hereditary diffuse gastric cancer, Peutz-Jeghers syndrome, Cowden syndrome, Neurofibromatosis type 1, or Fanconi anemia) are also recommended for annual screening MRI beginning between ages 20-35, depending on the mutation.¹⁴ Women with known pathogenic mutations in ATM, CHEK2, or NBN should consider annual MRI starting at age 40 or 5-10 years before the earliest known breast cancer in the family (whichever comes first). 

Finally, women with prior chest radiation therapy (such as for Hodgkin disease) between ages 10 and 30 are at high risk for developing breast cancer,^4,15,16 with risk similar in magnitude to pathogenic BRCA1 or BRCA2  carriers. These women are also recommended for annual screening MRI starting at age 25 or 8 years after the chest radiation therapy, whichever is later.

Currently the Tyrer-Cuzick Model (IBIS) version 817 and the Breast Cancer Surveillance Consortium (BCSC) models¹⁸ include breast density in risk calculations; the Gail, Penn II, and Claus models do not include breast density. 

Adding polygenic risk scores based on single nucleotide polymorphisms to traditional comprehensive risk models such as the Tyrer-Cuzick model has been shown to improve model performance.¹⁹ In addition, artificial intelligence is being used to identify textural and other findings beyond breast density on mammograms that predict increased risk. Such information, which is complementary to the Tyrer-Cuzick model (v.8),²⁰ has more accurately identified high-risk patients than the Tyrer-Cuzick v8 risk model and prior deep learning models.²¹ 

In a study from the Karolinska Institute, a model that included computer-aided detection of microcalcifications and masses in addition to other traditional risk factors (including breast density) successfully identified women who would develop interval or advanced cancer in the 2 years after a normal mammogram and improved short-term (2-to-3-year) risk assessment over TyrerCuzick (v.7) or Gail models.²² This model proved more accurate than traditional risk models and can augment genetic/family history to help identify women who should and, importantly, who should not, have supplemental screening after 2D mammography. Risk models that include detailed family history should be used rather than the Gail model to identify women who meet high risk criteria for MRI screening. Research also supports the benefits of MRI in women with dense breasts who are not otherwise considered “high risk,” and while not widely available, lower cost, abbreviated MRI protocols have been validated for all women with dense breasts.²³ For more details on risk models, including a risk models table with live links to commonly used breast cancer risk assessment tools, visit https://densebreast-info .org/for-providers/risk-model-tutorial/. ●

_{Text copyright DenseBreast-info.org.}

Answer

B.  The Gail risk model^1-3 is used to predict 5-year and lifetime risks of developing invasive breast cancer, and to identify women who may benefit from risk-reducing medications such as tamoxifen. The Gail model should not be used to determine risk for purposes of screening magnetic resonance imaging (MRI)⁴ (or genetic testing).

Breast cancer risk models are used to stratify patients into risk categories to facilitate personalized screening and surveillance plans for clinical management. Several breast cancer risk assessment tools have been developed that include different combinations of known risk factors and are used for the following purposes: 

1. To identify women who may benefit from risk-reducing medications. The Gail model is used to determine risk for purposes of advising on use of risk-reducing medications. Any woman with a 5-year risk ≥1.67% by the Gail model may be considered for treatment with tamoxifen (pre or postmenopausal), raloxifene (postmenopausal), or aromatase inhibitors (postmenopausal).⁵  

In the National Surgical Adjuvant Breast and Bowel Project (NSABP) P1 study,⁶ women at increased risk for breast cancer were defined as follows: 

• age 35 to 59 years with at least a 1.66% 5-year risk for developing breast cancer by the Gail model
• personal history of lobular carcinoma in situ (LCIS)
• age over 60 years.

More than 13,000 such women were randomly assigned to receive tamoxifen or placebo daily for 5 years. Tamoxifen reduced the risk of invasive breast cancer by 49% and reduced the risk of noninvasive cancer by 50% compared with placebo. The reduced risk of breast cancer was only seen for estrogen-receptor–expressing tumors. There was a 2.5-fold increase in risk of endometrial cancer in women taking tamoxifen and a decrease in hip and spine fracture risk. Blood clots causing stroke and deep vein thrombosis are increased in women taking tamoxifen.^7,8

2. To identify women who may carry a pathogenic mutation in BRCA1 or BRCA2. Some models (eg, Tyrer-Cuzick [IBIS],⁹ Penn II,¹⁰ BOADICEA,¹¹ and BRCAPRO¹²) estimate the probability of a BRCA1/2 mutation; however, most testing guidelines are now criterion based (eg, National Comprehensive Cancer Network [NCCN]) as opposed to probability based. In practical terms, clinical decision making around genetic testing is rarely based on a priori probabilities. 

3.  To identify women who meet criteria for high-risk screening MRI. Current American Cancer Society (ACS) guidelines⁴ recommend annual screening MRI, in addition to mammography, beginning by age 25 to 30 in women who have a lifetime risk of breast cancer ≥20%. Any of the models used to predict risk of a pathogenic mutation (Tyrer-Cuzick [IBIS], Penn II, BOADICEA, BRCAPRO),or the Claus model,¹³ but not the Gail model, can be used to estimate lifetime risk for purposes of screening MRI guidelines. The ACS and NCCN guidelines specifically recommend against using the Gail model to determine risk for purposes of MRI screening or risk of pathogenic mutation, as it does not include detailed family history such as age at diagnosis or second-degree relatives. 

ACS and NCCN guidelines also recommend annual screening MRI beginning by age 25, with the addition of mammography beginning at age 30, in women who are known to carry pathogenic mutations in BRCA1 or BRCA2 (unless the woman has had bilateral mastectomy), and in women who are first-degree relatives of known mutation carriers but who are themselves untested.¹⁴ 

Women who are known to carry or are first-degree untested relatives of individuals with less common disease-causing mutations (such as those associated with Li-Fraumeni syndrome, Bannayan-Riley-Ruvalcaba syndrome, hereditary diffuse gastric cancer, Peutz-Jeghers syndrome, Cowden syndrome, Neurofibromatosis type 1, or Fanconi anemia) are also recommended for annual screening MRI beginning between ages 20-35, depending on the mutation.¹⁴ Women with known pathogenic mutations in ATM, CHEK2, or NBN should consider annual MRI starting at age 40 or 5-10 years before the earliest known breast cancer in the family (whichever comes first). 

Finally, women with prior chest radiation therapy (such as for Hodgkin disease) between ages 10 and 30 are at high risk for developing breast cancer,^4,15,16 with risk similar in magnitude to pathogenic BRCA1 or BRCA2  carriers. These women are also recommended for annual screening MRI starting at age 25 or 8 years after the chest radiation therapy, whichever is later.

Currently the Tyrer-Cuzick Model (IBIS) version 817 and the Breast Cancer Surveillance Consortium (BCSC) models¹⁸ include breast density in risk calculations; the Gail, Penn II, and Claus models do not include breast density. 

Adding polygenic risk scores based on single nucleotide polymorphisms to traditional comprehensive risk models such as the Tyrer-Cuzick model has been shown to improve model performance.¹⁹ In addition, artificial intelligence is being used to identify textural and other findings beyond breast density on mammograms that predict increased risk. Such information, which is complementary to the Tyrer-Cuzick model (v.8),²⁰ has more accurately identified high-risk patients than the Tyrer-Cuzick v8 risk model and prior deep learning models.²¹ 

In a study from the Karolinska Institute, a model that included computer-aided detection of microcalcifications and masses in addition to other traditional risk factors (including breast density) successfully identified women who would develop interval or advanced cancer in the 2 years after a normal mammogram and improved short-term (2-to-3-year) risk assessment over TyrerCuzick (v.7) or Gail models.²² This model proved more accurate than traditional risk models and can augment genetic/family history to help identify women who should and, importantly, who should not, have supplemental screening after 2D mammography. Risk models that include detailed family history should be used rather than the Gail model to identify women who meet high risk criteria for MRI screening. Research also supports the benefits of MRI in women with dense breasts who are not otherwise considered “high risk,” and while not widely available, lower cost, abbreviated MRI protocols have been validated for all women with dense breasts.²³ For more details on risk models, including a risk models table with live links to commonly used breast cancer risk assessment tools, visit https://densebreast-info .org/for-providers/risk-model-tutorial/. ●

What are the most common organisms that cause chorioamnionitis and puerperal endometritis?

Continue to the answer...

Chorioamnionitis and puerperal endometritis are polymicrobial, mixed aerobic-anaerobic infections. The dominant organisms are anaerobic gram-negative bacilli (Bacteroides and Prevotella species); anaerobic gram-positive cocci (Peptococcus species and Peptostreptococcus species); aerobic gram-negative bacilli (principally, Escherichia coli, Klebsiella pneumoniae, and Proteus species); and aerobic gram-positive cocci (enterococci, staphylococci, and group B streptococci).