What is the greatest risk factor for meconium aspiration syndrome?

Meconium aspiration syndrome (MAS) occurs when a newborn inhales a mixture of meconium and amniotic fluid into the lungs around the time of delivery. The greatest risk factor for MAS is post-mature gestational age, which is defined as being beyond 42 weeks of pregnancy. As the gestation period extends, the likelihood of the fetus passing meconium increases. This can happen because the fetal stress related to post-maturity often leads to meconium-stained amniotic fluid. When the fetus inhales this stained fluid, the meconium can obstruct their airways and lead to respiratory distress, resulting in MAS.

In this context, although factors like multiple gestation, advanced maternal age, and maternal smoking can contribute to complications during pregnancy and delivery, they are not as directly linked to the incidence of meconium aspiration syndrome as post-maturity is. Hence, the association with post-mature gestational age is crucial in understanding the greatest risk for this condition.