Vaginal administration produces unpredictable peak times for estradiol in breast milk, so it is likely that the timing of the dose with respect to breastfeeding is not. Current evidence seems to indicate that combined oral contraceptives are unlikely to substantially affect the composition of milk in healthy, well-nourished mothers and do not adversely affect infant growth and development in the long term. Combined oral contraceptives may negatively affect growth transiently during the first month after their introduction. The magnitude of the effect on lactation is likely to depend on the dose and the time of introduction after delivery.
A treatment plan has been reported for mothers with hypergalactia in which low-dose combined oral contraceptives are used to reduce milk production. Ethinylestradiol in doses greater than 30 mcg per day may suppress lactation and cause more supplements to be administered and, possibly, breastfeeding to be stopped sooner than with non-hormonal or progestin-only contraceptives. In addition, administering estrogen before 3 weeks after delivery may increase the risk of thromboembolism in women who are giving birth. Rare cases of reversible breast enlargement have been reported in infants, mostly with doses of estrogen higher than those currently used.
Estrogen may mean that you produce less milk. So when you tell your doctor that you're breastfeeding, they'll likely recommend the minipill. It shouldn't affect your milk supply at all. During breastfeeding, estrogen levels in the body decrease and prolactin, the main hormone responsible for the production of breast milk, increases.
A topic that is often little discussed is how breastfeeding or pumping affect pelvic health and how estrogen influences it. Contraceptives containing estrogen are only recommended to be used with caution, especially in those mothers who have had problems with their milk production. The accumulated milk was bioanalyzed to determine its estrogenic activity and was compared with the milk of nursing mothers who did not take exogenous estrogens and whose milk was collected several times after delivery. A retrospective cohort study compared 371 women who received high doses of estrogen (3 mg of diethylstilbestrol or 150 mcg of ethinylestradiol per day) during adolescence to reduce their adult height with 409 women who did not receive estrogen.
You may notice a decrease in your milk supply after you start taking hormonal birth control pills (especially those that contain estrogen). Contraceptives containing estrogen have been linked to reduced milk production and premature cessation of breastfeeding, even when breastfeeding begins after milk production is well established and the baby is older. Estrogen can reduce milk production, especially if started before milk production is well established, about 6 weeks later of childbirth.
