Neonates from isoimmunized pregnancies have increased morbidity from neonatal jaundice. The increased bilirubin from haemolysis often needs phototherapy, exchange transfusion or both after birth. Various trials in pregnant women who were not isoimmunized but had other risk factors for neonatal jaundice have shown a reduction in need for phototherapy and exchange transfusion by the use of antenatal phenobarbital. A recent retrospective case-controlled study showed reduction in the need for exchange transfusion for the neonates from isoimmunized pregnancies. To assess the effects of antenatal phenobarbital in red cell isoimmunized pregnancies in reducing the incidence of phototherapy and exchange transfusion for the neonate. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (June 2006). Randomised and quasi-randomised controlled trials of pregnant women established to have red cell isoimmunization in the current pregnancy during their antenatal testing and given phenobarbital alone or in combination with other drugs before birth. All three review authors independently assessed study eligibility and quality. No trials met the inclusion criteria for this review. The use of antenatal phenobarbital to reduce neonatal jaundice in red cell isoimmunized pregnant women has not been evaluated in randomised controlled trials.