Modern, exogenous exposures associated with altered mammary gland development: A systematic review.

ABSTRACT

BACKGROUND: Many women report low milk supply as the reason for premature breastfeeding cessation. Altered mammary gland development may impact a woman's lactation ability. OBJECTIVE: This review identifies modern exogenous exposures which alter mammary gland development during embryonic life, puberty and pregnancy. METHODS: A systematic review was undertaken whereby Medline, CINAHL and Embase articles published from January 1, 2005 to November 20, 2020 were searched using the keywords puberty or embry* or fetal or foetal or foetus or fetus or pregnan* or gestation* AND "mammary gland development" or "breast development" or "mammary development" or "mammary gland function" or "mammary function" or "insufficient glandular tissue" or "mammary hypoplasia" or "breast hypoplasia" or "mammary gland hypoplasia" or "tubular breast*" or "tuberous breast*" or "glandular tissue" or "breast composition" or "mammary composition" or "mammary gland composition". After initial screening of 1207 records, 60 full texts were assessed for eligibility; 6 were excluded due to lack of information about exposure or outcome, leaving 54 studies. RESULTS: The review included results from 52 animal (rats and mice, monkeys, rabbits, sheep, goats pigs and cows) and 2 human studies. Various endocrine disrupting chemicals and an obesogenic diet were found to be associated with altered mammary gland morphology during key development stages. CONCLUSIONS: To improve lactation outcomes, future studies need to focus on lactation as the endpoint and be conducted in a standardised manner to allow for a more significant contribution to the literature that allows for better comparison across studies.