Estradiol Cypionate and Breastfeeding

Summary of use during lactation

Estradiol cypionate has not been studied during breastfeeding. However, a similar drug, estradiol valerate, has been used to suppress lactation. Estradiol cypionate should be avoided in mothers wishing to breastfeed, especially if started before the milk supply is well established at about 6 weeks postpartum. The decrease in milk supply can happen over the first few days of estrogen exposure.[1]

Drug levels in milk and infant serum

Maternal Levels. Relevant published information on estradiol cypionate was not found as of the revision date. However, estradiol appears in breastmilk in small amounts after administration by other routes.[2,3] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

A telephone follow-up of 16 women taking short-term high dose estradiol valerate found no adverse effects on appetite or growth in their breastfed infants at a median follow-up age of 13 months. The median age of the infant at the start of therapy was 2 months (range 1.5 to 4 months) and the median daily dose was 2 mg (range 1 to 4 mg).[4]

Effects on lactation and breastmilk

Another injection ester form of estradiol, estradiol valerate was previously used therapeutically to suppress lactation, usually in combination with testosterone.[5-7] A retrospective cohort study compared 371 women who received high-dose estrogen (either 3 mg of diethylstilbestrol or 150 mcg of ethinyl estradiol daily) during adolescence for adult height reduction to 409 women who did not receive estrogen. No difference in breastfeeding duration was found between the two groups, indicating that high-dose estrogen during adolescence has no effect on later breastfeeding.[8] Eight women taking estradiol valerate or estradiol hemihydrate in a median daily dose of 2 mg (range 1 to 4 mg) were followed up by telephone. The median time postpartum at the start of therapy was 2 months (range 1.5 to 4 months). The mean breastfeeding duration was 8.5 months. However, 8 of the women experienced a decrease in milk supply and 3 required supplementation with milk production not returning in these three.[4]

Alternative drugs to consider

Ethinyl Estradiol

References

1. Moses-Kolko EL, Berga SL, Kalro B, et al. Transdermal estradiol for postpartum depression: A promising treatment option. Clin Obstet Gynecol 2009;52:516-2919661765 PubMed
2. Nilsson S, Nygren KG, Johansson ED. Transfer of estradiol to human milk. Am J Obstet Gynecol 1978;132:653-7717472 PubMed
3. Perheentupa A, Critchley HO, Illingworth PJ, et al. Enhanced sensitivity to steroid-negative feedback during breast-feeding: Low-dose estradiol (transdermal estradiol supplementation) suppresses gonadotropins and ovarian activity assessed by inhibin B. J Clin Endocrinol Metab 2000;85:4280-611095468 PubMed
4. Shalit S, Yehuda S, De-Haan T, et al. High dose estrogen during breastfeeding-a prospective study. Neurotoxicol Teratol 2025;109 (Suppl 2):25-6.doi:10.1016/j.ntt.2025.107515
5. Louviere RL, Upton RT. Evaluation of Deladumone OB in the suppression of postpartum lactation. Am J Obstet Gynecol 1975;121:641-21090174 PubMed
6. Morris JA, Creasy RK, Hohe PT. Inhibition of puerperal lactation. Double-blind comparison of chlorotrianesene, testosterone enanthate with estradiol valerate and placebo. Obstet Gynecol 1970;36:107-144912251 PubMed
7. Iliya FA, Safon L, O'Leary JA. Testosterone enanthate (180 mg.) and estradiol valerate (8 mg.) for suppression of lactation: A double-blind evaluation. Obstet Gynecol 1966;27:643-55949195 PubMed
8. Jordan HL, Bruinsma FJ, Thomson RJ, et al. Adolescent exposure to high-dose estrogen and subsequent effects on lactation. Reprod Toxicol 2007;24:397-40217531440 PubMed