Is penicillin G a better choice than ampicillin for prophylaxis of neonatal group B streptococcal infections?

A review of the pharmacokinetics and the narrow spectrum of action of penicillin G favors this antibiotic over ampicillin for the prophylaxis of early neonatal group B streptococcal (GBS) disease. Penicillin G provides good placental transfer and fetal and neonatal tissue levels. Group B streptococcal disease has a narrower range of sensitivities to penicillin G than to ampicillin, and the potential for selecting more resistant organisms may be greater with the broader spectrum of ampicillin than with penicillin G.