neonatal mastitis (hormonal)

Last reviewed 01/2018

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

Notes:

• 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)

Reference:

• Niewoehner CB, Schorer AE. Gynaecomastia and breast cancer in men. BMJ. 2008 Mar 29;336(7646):709-13.
• Amer A, Fischer H. Images in clinical medicine. Neonatal breast enlargement. . N Engl J Med. 2009 Apr 2;360(14):1445