Patrick Duff M.D. highlights group B streptococcal infection in pregnancy. He describes the principal risk factors for early-onset group B streptococcal infection, the most useful methods for identifying maternal group B streptococcal colonization and the best strategies for reducing the frequency of early-onset neonatal group B streptococcal infection. Lastly, he shares the special considerations for antibiotic prophylaxis in patients who are allergic to penicillin.