Which condition poses the greatest risk for meconium aspiration in a newborn?

The condition that poses the greatest risk for meconium aspiration in a newborn is being born at more than 42 weeks' gestation. When a fetus is post-term, the likelihood of experiencing stress during labor increases, which can lead to the release of meconium into the amniotic fluid. Meconium aspiration occurs when a newborn inhales a mixture of meconium and amniotic fluid into the lungs at the time of birth, potentially causing severe respiratory complications.

In post-term pregnancies, the placental function may decline, leading to fetal distress. This distress can trigger the infant to pass meconium before or during labor. The greater the gestational age, the higher the risk of encountering complications associated with meconium aspiration.

Other conditions may be risk factors, but the direct correlation of a post-term birth significantly heightens the chance of meconium presence during delivery, making it the most critical factor among the options provided.