Breastfeeding women who are exclusively breastfeeding during the first 6 months have lower fertility because of the Lactation Amenorrhea Method (LAM), which prevents ovulation¹. A woman who is fully or nearly fully nursing (no more than 1-2 supplementary feedings each week), is amenorrheic, not taking long breaks from breastfeeding day or night, and is under 6 months postpartum meets the criteria for LAM, and has an approximately 2% risk of pregnancy without birth control.

Contraceptive options that do not have an impact on lactation include barrier methods, such as condoms, diaphragms, and spermicides, and the copper IUD. Any hormonal methods can impact the milk supply.

The onset of milk production postpartum relies on the declining levels of placental hormones, primarily progesterone. Any progesterone, testosterone, or estrogen hormones given before breastfeeding is well established, usually at approximately 6 weeks postpartum, increases the risk of insufficient milk supply². Current recommendations from the Center for Disease Control³ and The World Health Organization⁴ differ on timing for the safe introduction of progesterone-only birth control and the combined estrogen-progesterone birth control products.

Unfortunately, the overall evidence is poor regarding the effect of hormonal contraception on the milk supply. Because estrogen and progesterone can inhibit prolactin effectiveness at the lactocyte level, there is a risk of lower milk supply with introduction of hormonal contraceptive methods even beyond 6 weeks postpartum. Evidence shows that estrogen is more likely to drop the milk supply than progesterone-only methods⁵. Breastfeeding women need information to weigh the benefits of pregnancy protection with the risk of lower milk supply.

Many lactation specialists notice much less impact on milk supply with the progesterone IUD and the progesterone-only birth control pill when introduced at 6 weeks or later postpartum, in comparison with long acting progesterones. Placement of the progesterone IUD during the first few hours postpartum has not been well studied, and safety in terms of its effect on lactation has not been proven. The few studies done so far indicate that immediate postpartum placement of the progesterone IUD can be associated with insufficient milk supply.

Estrogen therapy is often quite effective to reduce milk supply at any time during lactation.

For more complete information on contraception during lactation, please see the Academy of Breastfeeding Medicine protocol entitled ‘Contraception During Lactation’ https://abm.memberclicks.net/assets/DOCUMENTS/PROTOCOLS/13-contraception-and-breastfeeding-protocol-english.pdf.