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Do Combined Oral Contraceptives Worsen Breastfeeding Outcomes?
Abstract & Commentary
By Jeffrey T. Jensen, MD, MPH , Leon Speroff, Professor and Vice Chair for Research, Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, is Editor for OB/GYN Clinical Alert.
Synopsis: Use of combined oral contraceptives instead of progestin-only pills does not worsen breastfeeding outcomes.
Source: Espey E, et al. Effect of progestin compared with combined oral contraceptive pills on lactation: A randomized controlled trial. Obstet Gynecol 2012;119:5-13.
The authors performed a randomized, double-blind study to compare the effects of progestin-only and combined hormonal contraceptive pills on rates of breastfeeding continuation in postpartum women. Important secondary outcomes included infant growth parameters, satisfaction with breastfeeding, and contraceptive method continuation and satisfaction.
Research nurses approached postpartum women aged 15-45 years who intended to breastfeed and who planned to use oral contraceptives (OC) as their family planning method prior to their hospital discharge. Those who were willing to be randomized to either a progestin-only pill or a combined pill were enrolled if there were no maternal contraindications to combined pills or neonatal concerns that might pose concerns for feeding. Consenting subjects were randomly assigned to receive either a progestin-only (0.35 mg of norethindrone) or combined (1 mg norethindrone/35 mcg ethinyl estradiol; 21 active pills, seven placebo pills) OC starting 2 weeks after delivery. Assignment was concealed by the research pharmacist who removed pills from their approved blister packs and then repackaged them in identical red plastic capsules placing them in identical monthly pill dispensers to disguise their appearance and to maintain the correct order of pill administration (for the standard 21/7 combined pill regimen). Prior to initiation of the pill at 2 weeks postpartum, participants completed in-person questionnaires that assessed breastfeeding continuation and contraceptive use. These were repeated at 8 weeks postpartum along with assessment of infant growth parameters including weight, length, and head circumference. Telephone questionnaires assessing breastfeeding, contraceptive continuation, and satisfaction were completed weekly between these visits, and at 4 and 6 months. Breastfeeding continuation at 8 weeks (compared between groups using Cox proportional hazards regression) did not differ between pill groups (progestin-only 63.5%; combined hormonal 64.1%), and there was no difference in contraceptive continuation or infant growth parameters. Factors associated with decreased rates of breastfeeding in both groups were infant formula supplementation and maternal perception of inadequate milk supply.
This well-designed clinical trial addresses the two most common discharge dilemmas on the postpartum unit for healthy mothers. How do we increase rates of breastfeeding and how do we improve contraceptive compliance to reduce the risk of unintended pregnancy? According to the most recent results of the National Survey of Family Growth, about 20% of women will want to use the pill.1 In many institutions, including my own, the postpartum discharge contraception discussion is relegated to interns, and we commonly recommend that women discontinue combined pills that they might be familiar with and like in favor of a progestin-only pill. Although we hope that this conversation is informed by upper-level residents and attending physicians practicing evidence-based medicine, frequently the routine nature of postpartum rounds to health care providers and the multiple distractions of new parents affect the quality of the interaction. The Espey study is notable as it attacks a well-established dogma with Level I evidence. The standard teaching is that estrogen adversely affects breast milk production. There is limited support for this hypothesis in the literature. An open-label, multicenter, World Health Organization (WHO) cohort study found that combined OCs caused a significant decrease in milk output and total energy content, as well as widespread changes in milk constituents, while none of these changes were observed in users of the progestin-only pill and depot medroxyprogesterone acetate. However, as the authors of the current study note in their discussion, the changes observed in the combined OC group were not associated with significant differences in infant weight or fat-fold, or in the rate of contraceptive discontinuation for failure to gain weight.2 A 2003 Cochrane review by Truitt concluded "evidence from randomized controlled trials on the effect of hormonal contraceptives during lactation is limited and of poor quality; results should be interpreted with caution. The existing randomized controlled trials are insufficient to establish an effect of hormonal contraception, if any, on milk quality and quantity. Evidence is inadequate to make recommendations regarding hormonal contraceptive use for lactating women. At least one properly conducted randomized controlled trial of adequate size is urgently needed to address this question."3
Although the Espey study provides this much-needed evidence to alleviate the concern that breastfeeding success is reduced by the early initiation of a combined pill, a couple of other findings are worth noting before we lecture the interns on tomorrow's rounds. First, the most important factors associated with breastfeeding discontinuation in the study were self-identified concerns about the adequacy of milk supply and the use of any supplemental feeding. These were not affected by the contraceptive pill used. My pet peeve on morning rounds is the absence of a response from the medical team when a new mother announces that she plans to use "bottle and breast." The presence of formula in the patient's room is a sure sign that lactation will end early, and this is an important counseling point if we want to increase nursing success. The authors mention that breastfeeding characteristics in the study population were similar to other women in New Mexico, where 84% initiate breastfeeding but only 60% continue to breastfeed through 8 weeks. In the study cohort, 64% of randomized study participants were breastfeeding at 8 weeks, but only 28% were exclusively breastfeeding. While this small number of exclusively breastfeeding moms potentially dilutes the overall impact of estrogen use on breastfeeding continuation, there did not appear to be any difference in continuation based on the pill used, regardless of whether there were concerns about milk supply or the use of supplements. Infant growth parameters did not differ between groups over 8 weeks.
Another important issue to consider is contraceptive efficacy. Women who exclusively breastfeed are at low risk for pregnancy during the first 4-6 months postpartum, while ovulation can occur as early as 3 weeks postpartum in non-breastfeeding women or as early as 6 weeks in women who are breastfeeding with supplementation.4 In patient populations where the expectation for breastfeeding is low, it makes sense to initiate contraception early, with the most effective and reliable method possible. For many women, that may be a combination OC, particularly if they have had good success with the method in the past. The typical failure with progestin-only pills is about the same as combination pills,5 so we should not hesitate to recommend these. However, the most important feature of success is correct and consistent use. The study was too small to consider pregnancy rates, but there was no difference in satisfaction or discontinuation of the contraceptive method. Unfortunately, the authors did not present any data beyond 8 weeks, where bleeding patterns become unsatisfactory for many women on the progestin-only pill.
My final point reflects the constant call of the physician to balance potential harm with potential good. Although the use of combined OCs may not affect success with breastfeeding or infant growth, is it safe for mothers? The WHO, Centers for Disease Control (CDC), and American Congress of Obstetricians and Gynecologists say no. The recently published CDC medical eligibility criteria (MEC) for contraceptive use assigns initiation of combined pills before 21 days postpartum as category 4 (unacceptable health risks) for thromboembolism, and initiation at 21-29 days for women at low risk (e.g., no other risk factors except recent delivery) for thromboembolism as category 3 (theoretical or proven risks generally outweigh advantages).6 The WHO MEC7 are even more conservative with a category 4 (unacceptable health risk) for initiation of combined pills within 6 weeks of delivery and a category 3 (theoretical or proven risks usually outweigh the advantages) for initiation of combined pills from 6 weeks to 6 months in primarily breastfeeding women. However, it is fair to point out that both of these recommendations are based on consensus opinion, as there is no direct evidence examining the risk for venous thromboembolism among postpartum women using combined pills.