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Neonatal gynaecomastia

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Neonatal gynaecomastia

  • Overall, 65-90% of neonates have breast tissue (1)
    • results from the transfer of maternal and placental oestrogen and progesterone
    • persists up to several months


  • neonatal breast enlargement is a normal response to falling levels of maternal estrogen at the end of pregnancy
    • these trigger the release of prolactin from the newborn's pituitary
  • neonatal breast enlargement is common is independent of the sex of the baby
  • generally bilateral - although may not be symmetrical; if unilateral then consider breast abscess; also infective mastitis can occur in a neonate and consider this especially if neonate is unwell and breast enlargement has features of infection (e.g. heat, erythema)
  • usually occurs in the first week of life and generally resolves within a few weeks (2) - but may persist for several months (1)
  • enlarged breast may discharge liquid; this usually resolves without treatment over a period of a few weeks
    • squeezing the breast to facilitate the discharge may lead to irritation, further enlargement, the persistence of the hypertrophied tissue, or, in rare cases, infection (mastitis or abscess)


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