DefinitionMeconium aspiration syndrome is a serious condition in which a newborn breathes a mixture of meconium and amniotic fluid into the lungs around the time of delivery.Alternative NamesMAS; Meconium pneumonitis (inflammation of the lungs)Causes, incidence, and risk factorsMeconium is the term used for the early feces (stool) passed by a newborn soon after birth, before the baby has started to digest breast milk (or formula).In some cases, the baby passes stools (meconium) while still inside the uterus. This usually happens when babies are under stress because they are not getting enough blood and oxygen.Once the meconium has passed into the surrounding amniotic fluid, the baby may breathe meconium into the lungs. This may happen while the baby is still in the uterus, or still covered