Monarch Disease Ontology id MONDO_0006851 (meconium aspiration syndrome) is a serious condition in which a newborn breathes a mixture of meconium (the first intestinal discharge) and amniotic fluid into the lungs around the time of delivery. Meconium aspiration syndrome occurs in 5-10 percent of births and typically occurs when the infant is stressed, as when the infant is past its due date. Also known as: MAS, meconium aspiration, neonatal aspiration of meconium.