Hormonal Contraception and Breastfeeding

Hormonal Contraception and Breastfeeding

Abstract & Commentary

By Jeffrey T. Jensen, MD, MPH, Editor

Synopsis: Infants of women initiating either a combined oral contraceptive, the levonorgestrel IUS, the etonogestrel implant, or a copper IUD at 42 days postpartum ingested similar volumes of breast milk and displayed similar growth. Neither breastfeeding patterns nor continuation were influenced by the type of contraception.

Source: Bahamondes L, et al. Effect of hormonal contraceptives during breastfeeding on infant's milk ingestion and growth. Fertil Steril 2013;100:445-450.

Despite lack of strong evidence of a deleterious ef-
fect, many clinicians are reluctant to use combined hormonal contraception (CHC) in breastfeeding women. The concern is that estrogen will reduce breast milk volume and the success of nursing. In fact, the World Health Organization (WHO) Medical Eligibility Criteria (MEC) for contraception lists initiation of combined hormonal methods in breastfeeding women > 6 weeks but < 6 months postpartum as Category 3 (condition where the theoretical or proven risks usually outweigh the advantages of using the method). Although the Centers for Disease Control and Prevention (CDC) MEC does not restrict use of CHCs in breastfeeding women beyond 4 weeks postpartum, the absence of a definitive, well-designed, randomized trial makes the issue controversial. While the study by Bahamondes and colleagues does not provide this definitive answer, it offers a novel technique to address the question of milk volume and infant growth.

The investigators recruited healthy multiparous women and newborns after a term vaginal delivery at a university hospital. To be eligible, the women needed to have had prior experience with breastfeeding and an interest in exclusively nursing the infant (no supplements) during the study period. The mothers returned to the outpatient clinic on postpartum day 42 to initiate a contraceptive method of their choice; either a combined pill (COC) containing 150 mcg levonorgestrel (LNG) and 30 mcg ethinyl-estradiol (EE) in a 21/7 regimen, the LNG-IUS, the etonogestrel (ENG) implant, or the TCu380A copper IUD. The women were weighed before starting the contraceptive methods. To determine milk intake, the investigators administered deuterium "heavy water" (D2O) to the mothers. Deuterium is not radioactive and is completely safe. However, the extra proton can be easily detected using mass spectrometry, and the ratio of D2O to H2O calculated to determine volume. The investigators used a known initial volume and distribution in the mother to calculate the amount of D2O in the saliva of the infants and the mothers 30 minutes after a breastfeeding episode on postpartum days 43, 44, 45, 52, 53, 54, 56, 58, 60, and 63 at home. The infants' weights and heights were also measured on postpartum day 42 (baseline) and on days 52 and 63 after delivery.

While there was variation between the groups, when the COC group was compared with the progestin-only (LNG IUS and implant) and copper IUD groups, there was no difference in breast milk intake, infant growth, or success of nursing in the cohort.

Commentary

The successful initiation of a contraceptive method postpartum provides a myriad of benefit to families. Repeat pregnancy within 1 year of delivery is associated with poor perinatal outcomes.¹Barriers to initiation of a method of choice may reduce the uptake of contraception. While it is common practice in the United States to initiate the progestin-only pill (POP) to breastfeeding women, and then switch the pill after 6 months (or when breastfeeding ceases to be the exclusive food source for the infant), there is no strong evidence to support this approach. Women may not call back to change the pill, and since the only POP available in the United States requires meticulous compliance to be most effective, women may be exposed to an increased risk of pregnancy or discontinue the method due to unsatisfactory bleeding.

The elegant study by Bahamondes and colleagues provides additional evidence to support an absence of suppression of normal lactation by combined hormonal methods. Although the sample of women-infant dyads is small for all methods and the allocation of treatment was open label and non-randomized, the resolution of volume measurements made possible through the use of D2O was excellent. The results provide a supplement to the randomized study of COCs and POP reported by Espey et al last year.²Based on these two studies, clinicians should feel comfortable to initiate a combined hormonal method at 4-6 weeks postpartum. For exclusively breastfeeding women, there is no need to initiate a method prior to that time.

But since many women may not follow exclusive breastfeeding rules and also may engage in coital activity prior to the 6-week interval, is it safe to start a combined method earlier than the routine postpartum check-up? The WHO, CDC, and ACOG all say no. The concern is not breastfeeding success but venous thromboembolism (VTE). The recently published CDC MEC for contraceptive use assigns initiation of combined pills before 21 days postpartum as category 4 (unacceptable health risks) and initiation at 21-29 days for women at low risk (e.g., no other risk factors except recent delivery) for thromboembolism is rated category 3 (theoretical or proven risks generally outweigh advantages).³The WHO MEC⁴are even more conservative, with a category 4 (unacceptable health risk) for initiation of combined pills within 6 weeks of delivery. While there is no direct evidence examining the risk for VTE among postpartum women using combined pills, this is a high-risk period for VTE independent of CHC use and it makes sense to be cautious. Fortunately, there is no downside to the early use of the implant or an IUD!

References

1. Salihu HM, et al. The impact of birth spacing on subsequent feto-infant outcomes among community enrollees of a federal healthy start project. J Community Health 2012;37:137-142.
2. Espey E, et al. Effect of progestin compared with combined oral contraceptive pills only: A randomized controlled trial. Obstet Gynecol 2012;119:5-13.
3. Centers for Disease Control and Prevention (CDC). Update to CDC's U.S. Medical Eligibility Criteria for Contraceptive Use, 2010: Revised recommendations for the use of contraceptive methods during the postpartum period. MMWR Morb Mortal Wkly Rep 2011;60:878-883.
4. World Health Organization. Medical Eligibility Criteria for Contraceptive Use. 4th ed. 2009. Available at: www.who.int/reproductivehealth/publications/family_planning/9789241563888/en/index.html.