Why are a newborn’s breasts swollen?

What does the evidence show for newborn breast swelling?

• Maternal hormone exposure can cause breast tissue to become noticeable during the first days after birth. A small amount of milky nipple fluid may also occur. These changes are not a reason to express milk from the baby’s breasts. 1
• Normal enlargement generally settles with time, although the duration varies. Pressing or squeezing does not make the swelling disappear faster and can irritate the area. Show the pediatrician a persistent or changing lump rather than repeatedly checking it with pressure. 2
• Neonatal breast infection can involve redness, warmth, pain or pus and may develop into an abscess. A clinical series documents these findings in young infants, including some without fever. The absence of fever therefore should not be used to dismiss a worsening local change. 3
• Massage and attempts to empty the breast can introduce problems rather than help normal hormone-related swelling. Leave the tissue alone and use ordinary gentle skin care. If fluid looks bloody or purulent, or the area becomes painful, ask for clinical assessment. 1
• For a baby under three months, a rectal temperature of 100.4°F or higher requires immediate medical advice. Poor responsiveness, breathing difficulty or marked illness needs emergency attention. Do not wait for breast swelling to resolve before responding to systemic symptoms. 4

When should I call my provider about newborn breast swelling?

Arrange prompt assessment for increasing redness, warmth, pain, pus or rapidly worsening swelling, even without fever. A rectal temperature of 100.4°F or higher in a baby under three months needs immediate medical advice. Call emergency services for breathing difficulty or a baby who cannot be awakened.