Meconium aspiration syndrome

MAS; Meconium pneumonitis (inflammation of the lungs); Labor - meconium; Delivery - meconium; Neonatal - meconium; Newborn care - meconium

Meconium aspiration syndrome (MAS) refers to breathing problems that a newborn baby may have when:

  • There are no other known causes of symptoms
  • The baby has passed meconium (stool) into the amniotic fluid during labor or delivery

MAS may occur if the baby breathes (aspirates) this fluid into the lungs.


The first bowel movement a baby has is called meconium. Meconium is composed of amniotic fluid, mucus, lanugo (the fine hair that covers the baby's body), bile, and cells that have been shed from the skin and the intestinal tract. Meconium is thick, greenish black, and sticky.



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Outlook (Prognosis)