Meconium is the earliest stool of a newborn. Occasionally, newborns pass meconium during labor or delivery, resulting in a meconium-stained amniotic fluid (MSAF). Meconium aspiration syndrome (MAS) is the neonatal respiratory distress that occurs in a newborn in the context of MASF when respiratory symptoms cannot be attributed to another etiology. The spectrum of manifestations associated with meconium aspiration is broad, ranging from mild distress to more severe respiratory failure. More life-threatening conditions have been recognized to also be associated with MAS, notably persistent pulmonary hypertension of the newborn (PPHN), and air leak syndromes.