Pathophysiology and prevention of meconium aspiration syndrome.

Aspiration of meconium by the fetus at or near delivery may be associated with high infant morbidity and mortality. The meconium aspiration syndrome (MAS) is often preventable, yet cases of MAS continue to occur. This paper describes the pathophysiology of MAS. The development of MAS involves passage of meconium by a compromised fetus and the subsequent aspiration of that meconium. Respiratory tract obstruction, hypoxia, hypercapnia, and acidosis may all result. Treatment of MAS is primarily supportive, and high mortality rates have been reported with the more severe cases. There is good evidence that careful suctioning of the infant's upper respiratory tract can in most cases prevent MAS. The suctioning, performed while the infant's head is still on the mother's perineum and prior to the first inspirations, is both a safe and effective preventive procedure.