Meconium Aspiration Syndrome (MAS)
Neonatal aspiration of meconium
Meconium aspiration syndrome (MAS) also known as neonatal aspiration of meconium is a medical condition affecting newborn infants. It occurs when meconium is present in their lungs during or before delivery. Meconium is the first stool of an infant, composed of materials ingested during the time the infant spends in the uterus. Fetal distress during labor causes intestinal contractions, as well as relaxation of the anal sphincter, which allows meconium to pass into the amniotic fluid and contaminate the amniotic fluid. Meconium passage into the amniotic fluid occurs in about 5–20 percent of all births and is more common in overdue births.