Antenatal phenobarbital and bilirubin metabolism in the very low birth weight infant.

Prior studies in term infants have suggested that in utero phenobarbital exposure may accelerate bilirubin metabolism by stimulating hepatocyte glucuronyl transferase activity. This report reviews our experience with maternal phenobarbital therapy and fetal bilirubin conjugation in the very premature fetus. Mothers with arrested premature labor between 26 and 33 weeks' gestation were randomly assigned to receive oral phenobarbital (90 mg daily) or not. Infants in the two groups were similar in race, birth weight, and gestational age. Conjugated bilirubin levels at birth were significantly higher for infants receiving several days of phenobarbital in utero than no therapy (0.31 +/- 0.03 vs 0.16 +/- 0.01 mg dl, p less than 0.01). A smaller portion of infants exposed to phenobarbital in utero required phototherapy (10/23, 43% vs 24/29, 83%, p less than 0.01), which was also more likely to be delayed beyond 48 hours after delivery. Antenatal phenobarbital enhances bilirubin conjugation before delivery of a very low birth weight infant.