Time of first stool in premature infants: effect of gestational age and illness severity

To assess the effect of gestational age and illness severity, and the effect of antenatal exposure to magnesium sulfate and glucocorticosteroids, on the timing of the first stool in preterm infants.

Medical records of all preterm infants (born at < or = 36 weeks of gestational age) admitted to the neonatal intensive care unit at Georgetown University Hospital between April 1993 and March 1994 were reviewed. We studied the time of the first stool in 221 infants after removing from the investigation the 45 infants who met the exclusion criteria.

The median age of the infants at the time of the first stool was 18 hours, and 90% of the infants passed stool by 100 hours after birth. Both the gestational age and the illness severity, as measured by the Score for Neonatal Acute Physiology (SNAP), independently correlated with the timing of first stool (r = 0.31 and p < 0.0001 for gestational age; r = 0.33 and p < 0.0001 for SNAP). Of the 221 infants, 172 (78%) passed stool before the initiation of enteral feeding. Antenatal exposure to magnesium sulfate for tocolysis had no effect on the timing of the first stool, whereas infants whose mothers received glucocorticosteroids for enhancing fetal lung maturity passed their first stool significantly earlier than nonexposed infants of identical gestational age (p = 0.005).

Delayed passage of first stool is a function of both illness severity and gestational immaturity. Antenatal betamethasone exposure leads to earlier stool passage, whereas antenatal exposure to magnesium sulfate does not affect the timing of first stool in premature infants.