Two strategies for chemoprophylaxis of neonatal GBS disease have proven efficacy. Selective intrapartum chemoprophylaxis based on prenatal cultures and maternal risk factors (Boyer, Gotoff: NEJM 314:1665, 1986) is effective in high-risk deliveries. It is limited because prenatal cultures obtained at 26-28 weeks have suboptimal predictive value (60-70%) and because 30-50% of cases occur in babies without risk factors. Universal postnatal prophylaxis(Siegel et al: Lancet i: 1426, 1982) has 80% preventive efficacy in uncomplicated deliveries. It may be ineffective against infections established intrapartum in high-risk deliveries. The Centers for Disease Control (MMWR 45[RR-7]:1, 1996) have recently advocated intrapartum chemoprophylaxis for all deliveries in which the mother has either prenatal colonization at 35-36 weeks or perinatal risk factors. As an alternative to the CDC strategy, we recommend a combined approach in which cultures are obtained at 35 weeks and intrapartum chemoprophylaxis is given to colonized women with risk factors (premature labor or prolonged membrane rupture) and to other women with risk factors and unknown colonization status. Postpartum chemoprophylaxis is given to all normal newborns of untreated women with colonization. Febrile women in labor with presumed chorioamnionitis are treated (not prophylaxed) regardless of their colonization status, with cultures obtained prior to initiation of therapy. This combined approach is likely to have equal efficacy (90%) to the CDC strategy. However, it will reduce the predicted number of cases of maternal anaphylaxis from 140 to 40/year (by 70%), and reduce the predicted cost of the program from $250 million to $144 million/year (by 42%).
