Neonatal gynecomastia is usually transient due to exposure to which hormone, and when does it typically resolve?

• A. Maternal estrogen exposure; resolves by 4-8 weeks
• B. Infant testosterone deficiency; persists into childhood
• C. Breast milk production requiring observation for months
• D. Surgical treatment is required

Answer: (A)

Neonatal gynecomastia results from maternal estrogen exposure crossing the placenta and stimulating the newborn’s breast tissue; it is usually transient, resolving within 4–8 weeks after birth as the maternal hormones clear from the baby’s system. As estrogen levels drop and the infant’s hormone balance stabilizes, the enlarged tissue regresses on its own without treatment. This is not caused by infant testosterone deficiency, breast milk production, or requiring surgery, all of which do not fit the typical postnatal hormonal clearance pattern.