Which statement is true about meconium stained amniotic fluid (MSAF)?

• A. MSAF is highly predictive of fetal distress
• B. Incidence of MSAF decreases with increasing gestational age
• C. MAS occurs in only 40% of patients born through MSAF
• D. MSAF has no relation to fetal distress

Answer: (C)

Meconium in amniotic fluid signals that the fetus passed stool in utero, but it does not automatically cause trouble for every baby. The key point is that meconium staining is a risk marker, while meconium aspiration syndrome (MAS) is a complication that develops in only a portion of those exposed to meconium. In many cases, babies with MSAF are born well and do not develop MAS; in others, MAS can occur if meconium is aspirated and leads to airway obstruction and inflammation.

The statement that MAS occurs in only about 40% of patients born through MSAF reflects this idea: not all infants exposed to meconium go on to have MAS. The other options overstate the predictive value of MSAF for fetal distress (MSAF does not guarantee distress), misstate how the incidence of MSAF changes with gestational age (it tends to be more common with post-term pregnancies), or suggest there’s no relation to fetal distress (MSAF can be associated with distress).