Meconium

Meconium is a newborn’s first poop. This sticky, thick, dark green poop is made up of cells, protein, fats, and intestinal secretions, like bile. Babies typically pass meconium (mih-KOH-nee-em) in the first few hours and days after birth. But some babies pass meconium while still in the womb during late pregnancy.

Meconium aspiration syndrome (MAS) happens when a newborn has trouble breathing because meconium got into the lungs.

Meconium can make it harder to breathe because it can:

• clog the airways
• irritate the airways and injure lung tissue
• block surfactant, a fatty substance that helps open the lungs after birth

Meconium aspiration happens when a baby is stressed and gasps while still in the womb, or soon after delivery when taking those first breaths of air. When gasping, a baby may inhale amniotic fluid and any meconium in it.

Babies are more likely to pass meconium when:

• They’ve had a long or hard delivery.
• They are born past their due date.
• The mother has a health problem, like diabetes or high blood pressure.
• The mother smoked or used drugs during the pregnancy.
• They didn’t grow well before birth.