Clinical Review
The short cervix and preterm birth: 8 key questions and evidence-based answers
An expert review of screening, identification, and management for both nulliparous women and those with a history of spontaneous preterm birth
“Viable intrauterine pregnancy is possible in patients with pregnancy of unknown location and hCG levels above the generally accept discriminatory zone, strict adherence to which can potentially disrupt a normal pregnancy. We support the need for judicious use of the hCG discriminatory level in hemodynamically stable patients with pregnancy of unknown location, and the decision to intervene should not be based solely on a single hCG level.”
—Ko and Cheung.5
References
- Mehta TS, Levine D, Beckwith B. Treatment of ectopic pregnancy: is a human chorionic gonadotropin level of 2,000 mIU/mL a reasonable threshold? Radiology. 1997;205(2):569–573.
- Condous G, Kirk E, Lu C, et al. Diagnostic accuracy of varying discriminatory zones for the prediction of ectopic pregnancy in women with pregnancy of unknown location. Ultrasound Obstet Gynecol. 2005;26(7):770–775.
- Doubilet PM, Benson CB, Bourne T, et al. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013;369(15):1443–1451.
- Barnhart KT. Early pregnancy failure: beware of the pitfalls of modern management. Fertil Steril. 2012;98(5):1061–1065.
- Ko JK, Cheung VY. Time to revisit the human chorionic gonadotropin discriminatory level in the management of pregnancy of unknown location. J Ultrasound Med. 2014;33(3):465–471.
Stop using the discriminatory zone and a single hCG measurement to trigger clinical intervention As noted above, a single hCG measurement is of very little value in determining whether an early pregnancy is a viable or nonviable intrauterine pregnancy or is ectopic. Many experts have reported that if a single hCG measurement shows a value of more than 1,500 mIU/mL and a pelvic ultrasound shows no intrauterine pregnancy, an ectopic or nonviable intrauterine pregnancy is likely. Some experts have used the presence of an hCG value of more than 1,500 mIU/mL plus an ultrasound scan without evidence of an intrauterine pregnancy to clinically diagnose the absence of a viable intrauterine pregnancy and administer methotrexate to treat a presumptive ectopic pregnancy. Many experts believe, however, that this approach will necessarily result in the treatment of viable intrauterine pregnancies with methotrexate.5,10
Based on one analysis, for 100 women with an initial hCG value between 2,000 and 3,000 mIU/mL and no intrauterine pregnancy or adnexal mass seen on ultrasound, follow-up will reveal that 65.5% had a failed intrauterine pregnancy, 33% had an ectopic pregnancy, and 1.5% had a viable intrauterine pregnancy.3,10,11 If all of these 100 women had been treated with methotrexate for a presumed ectopic pregnancy, approximately two women with a viable intrauterine pregnancy would have been exposed to methotrexate. This exposure would likely result in either a pregnancy loss or, if the pregnancy continues, an increased risk of fetal anomalies.
If the patient is obese, has fibroids, or has adenomyosis, she has an increased risk of an ultrasound failing to detect an early intrauterine pregnancy when the hCG value ranges from 1,500 to 3,000 mIU/mL.12 If the discriminatory zone is raised to 4,000 mIU/mL, the likelihood of mistakenly diagnosing a viable intrauterine pregnancy as a failed or ectopic pregnancy is much less (but not zero).
There is almost no clinical situation in which methotrexate should be given to a patient suspected of having an ectopic pregnancy on the first visit, unless ultrasound demonstrates an adnexal mass indicative of ectopic pregnancy.13,14 If the patient has severe pain or bleeding, or has signs consistent with a ruptured ectopic pregnancy, surgical intervention likely is warranted. If the patient is clinically stable, a safe option is to repeat the hCG measurement in 48 hours, with an ultrasound if indicated.
The discriminatory zone is an interesting and elegant idea. But in practice it is fraught with serious dangers, the greatest of which is methotrexate administration to a patient with a viable intrauterine gestation. My advice is that gynecologists should stop relying on a discriminatory zone of 1,500 to 2,000 mIU/mL to trigger clinical intervention.
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