Exposure to contraceptive hormones through breast milk — are there longterm health and behavioral consequences?

Abstract

Lactating women who ingest contraceptive sex hormones secrete them or their metabolites in breast milk. The concentration of contraceptive hormones in milk varies from 10-100% of its concentration in the mothers plasma. After contraceptive injections very high plasma levels of hormone are found such that breast-fed children may be exposed to significant levels of hormones. Similar exposure may occur in children whose mothers receive hormone-impregnated intrauterine or vaginal contraceptives. Gynecomastia has been reported as an immediate consequence. Women also secrete natural sex hormones and gonadotrophins into milk. Little is known about what eventually happens to exogenous sex hormones in an infants body after being ingested through breast milk. It may be assumed that a proportion of the hormones is absorbed by the intestine and subsequently metabolized. Some portion of the hormones or their metabolites may however continue to circulate in the body of the infant where they may compete with natural hormones for receptor sites in sex organs brain and other tissue. The potential for ongoing circulation may be significant given the possibly lower metabolic rate of the infants immature liver. It is unknown whether a child will suffer any long-term consequences from breast milk exposure to contraceptive steroids. Of particular concern is the possible effect upon personality behavior sex organ anatomy reproductive ability immunologic function and neoplasia. Literature on animal research indicates the existence of long-term effects from exposure to certain hormones at critical periods of intrauterine and postnatal life and compatible results have been reported in limited research in humans exposed in utero suggesting that similar consequences may follow postnatal exposure to hormones in humans. The author summarizes existing knowledge on the effects of perinatal sex hormone exposure in animals and humans suggesting ways to study possible long-term consequences of exposure to contraceptives in breast milk.