Practice recommendations
- Lack of adherence is a common cause of breakthrough bleeding. Focus counseling on ensuring that patients understand and can follow pill-taking instructions before switching pills or method (A).
- If breakthrough bleeding extends beyond 4 cycles and a woman wish to continue using oral contraceptives, consider switching to a pill with a higher ethinyl estradiol (EE):progestin ratio, either by increasing the EE dose or decreasing the relative progestin dose (C).
- Breakthrough bleeding may be due to progestin type; switching from an estrane to a gonane may reduce it (C).
- Women who have breakthrough bleeding after having well-controlled menstrual cycles on oral contraceptives should be assessed for for causes not related to their birth control pills, such as pregnancy, cervicitis, smoking, or interactions with medications (A).
In 1982, more than 20% of women surveyed in a nationally representative sample had discontinued oral contraceptives (OCs) on their own or at the recommendation of their physician due to bleeding or spotting.1 Sadly, the percentage today has not decreased much.
Understandable concern, embarrassment, and annoyance lead these women to abandon OCs.1,2 What they often don’t know, though, is that breakthrough bleeding generally is greatest in the first 3 to 4 months after starting OCs,3 and it steadily declines and stabilizes by the end of the fourth cycle.4 Timely counsel could enable many of these women to cope with the bleeding and stick with an effective contraceptive method. Additional incentives are noncontraceptive benefits of OCs: improved menstrual regularity and decreased menstrual blood loss, dysmenorrhea, and risk of ovarian and endometrial cancer.
Women who discontinue OCs on their own switch to less effective methods of birth control or use no method.1,2 Consequences may be unexpected pregnancies and increased abortion rates.5 With patients who are using OCs, it would be appropriate to ask periodically whether they are satisfied with OC use.
In this review we discuss the mechanisms and management of breakthrough bleeding in women taking OCs, and provide tips for counseling that may help decrease the risk of discontinuation due to menstrual abnormalities in the initial months of use.
Breakthrough bleeding in this review refers to either unplanned spotting or bleeding, regardless of requirement for protection—unless defined otherwise by a specific study under discussion.
4 factors contribute to breakthrough bleeding
Breakthrough bleeding may be due to any the following factors: 1) physiologic effects of OCs on the endometrium, 2) OC-related parameters, including dose, formulation, and regimen, 3) patient behavior, including compliance, using concomitant medications, and smoking, and 4) benign or malignant pathology.
OCs and the endometrium: Estrogen-progestin balance significant
Progestin and estrogen in combination OCs have profound effects on the endometrium, which, though not contributing to contraception, do lead to a predictable pattern of bleeding or such problems as breakthrough bleeding or lack of withdrawal bleed.
Normally, estrogen causes the endometrium to proliferate. Progesterone stabilizes the growing uterine lining. Since the introduction of OCs in 1960, the trend in formulation has been to use the least amount of hormone necessary to inhibit ovulation. Given that the progestin is primarily responsible for the contraceptive efficacy of OCs, the risk of pregnancy is not altered with decreases in the estrogen component. However, significantly lowering the estrogen in OCs may account for breakthrough bleeding. Unplanned bleeding, though, is not dependent solely on the estrogen component as variations in the progestin can contribute to breakthrough bleeding.7
Most OC users in the US take low-dose formulations, so designated because the estrogen component is <50 μg. This level of estrogen in combination with a progestin provides excellent contraceptive efficacy, but may be insufficient to sustain endometrial integrity in some women.8 Studies that have compared OCs containing 20 μg ethinyl estradiol (EE) with those containing 30 μg or 35 μg EE have not been very useful for judging breakthrough bleeding rates because the products often also vary in the phasing and type of progestin. Some studies show more breakthrough bleeding with 20 μg EE pills,9-11 but others show equal or improved cycle control with the lower EE dose.
How is irregular bleeding defined?
For the purpose of performing studies, unplanned bleeding is classified by the World Health Organization into 2 categories: 1) breakthrough bleeding, which requires sanitary protection, and 2) spotting, which does not require sanitary protection.6 Despite this formal classification, trials have varied in their terminology and method of recording menstrual irregularities, making comparisons between studies difficult. In addition, there is wide variation among women in tolerance to bleeding abnormalities, perceptions of heavy vs light bleeding, as well as the need for protection.3
Nevertheless, menstrual abnormalities are consistently cited as a common reason for discontinuing OCs. A prospective US study of 1657 women performed in the 1990s reported that 37% of OC users had stopped taking OCs by 6 months after starting a new prescription because of side effects.2 Irregular bleeding was the most common cause; cited by 12% of women, followed by nausea, weight gain, and mood changes, which ranged from 5% to 7%.