Late third-trimester treatment of rectovaginal group B streptococci with benzathine penicillin G

Objective: We sought to determine the efficacy of late third-trimester benzathine penicillin G administration in eradicating maternal group B streptococcal colonization at delivery. Study Design: We performed a prospective trial of late third-trimester treatment with benzathine penicillin G versus observation in 78 obstetric patients colonized with group B streptococci. Patients were screened by use of rectovaginal swabs cultured in selective media between 34 and 37 completed weeks' gestation. Patients with positive cultures were offered antepartum treatment with 4.8 million units of intramuscular benzathine penicillin G or observation. Participants in both groups were recultured at their delivery admission before receiving standard intrapartum therapy. The primary outcome was the frequency of persistent maternal group B streptococcal colonization at the delivery admission. Other outcome variables included semiquantitative growth characteristics of all group B streptococcal cultures, the frequency of neonatal sepsis, and adverse maternal effects. Data were analyzed by the Student t test for continuous variables and the χ2 or Fisher exact test for categoric variables, with significance established at P