Ethinylestradiol

Synthetic estrogen that has a similar action as estradiol. Used in combination with progestogens for contraception. Daily oral administration.

ESTROGEN and related drugs are excreted into the breast milk in no or small amount.

Its pharmacokinetic data (high percentage of protein binding and very wide volume of distribution) explain the negligible or null passage into breast milk observed. ^{(Betrabet 1986, Nilsson 1978)}

Estrogens, alone or associated with progestogens, have been used in the treatment of excess milk production^{(Johnson 2020)} and to suppress lactation ^{(Piya 2004, Balmer 1971)}, although with very little effectiveness. ^{(Kaern 1967)}

There is evidence (albeit inconsistent) that estrogen-containing pills may decrease milk production or the duration of breastfeeding, especially if given during the first few weeks postpartum with a daily dose equal to or greater than 30 micrograms (0,03 mg) diarios. ^{(WHO 2002, AAP 2001, Moretti 2000, WHO 1988, Nilsson 1986, Tankeyoon 1984, Díaz 1983, Peralta 1983, Croxatto 1983, Guiloff 1974, Kaern 1967)}

Treatment with high doses of estrogens during adolescence does not affect later ability to breastfeed. ^{(Jordan 2007)}

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No short-term or long-term clinical, physical or psychomotor developmental problems have been observed in infants whose mothers were taking combined oral contraceptives ^{(Nilsson 1986)}, except for a few cases published years ago of transient gynecomastia in infants whose mothers were taking a combined oral contraceptive with ethinyl estradiol. ^{(Madhavapeddi 1985, Nilsson 1978, Marriq 1974, Curtis 1964)}

Hormonal contraceptives, both combined and progestogen-only, do not alter the composition of milk, neither in minerals (Mg, Fe, Cu, Ca, P) nor in fats, lactose, proteins or calories. ^{(Urzica 2013, Dórea 2000, 1999 y 1998, Costa 1992)}

No study has found negative effects on breast milk production or infant weight gain when combined oral contraceptives (estrogen + progestin) are started after the first 2, or better 6, weeks postpartum. ^{(Tepper 2015, Espey 2012)}

During lactation progestin-only drugs are preferred or in combination with estrogen for birth control, but whatever, the ones with the lower doses of estrogen should be used. ^{(CDC 2016, 2013 y 2010, WHO 2015, Berens 2015, CLM 2012)}

For the first 6 weeks postpartum, non-hormonal methods are of choise. ^{(Berens 2015, Rowe 2013)}