Antenatal phenobarbital for prevention of intraventricular hemorrhage in preterm infants

One of my patients, a 36-year-old, who has had three pregnancies and two live births, delivered her third baby at 32 weeks' gestation. Her first pregnancy was complicated by premature labour, which led to delivery at 30 weeks' gestation. She received antenatal phenobarbital before the first delivery because it was considered proven therapy for preventing intraventricular hemorrhage in preterm infants. I would like to know why it is no longer routinely used.

Cumulative results from recent studies have failed to confirm the initial impression of effectiveness of antenatal phenobarbital. It is no longer recommended when preterm delivery is anticipated.