Accuracy of prenatal culture in predicting intrapartum group B streptococcus colonization status

Objective: To evaluate the positive predictive value (PPV) of group B Streptococcus (GBS) cultures at 35–37 weeks of gestation relative to GBS colonization status at delivery. Methods: Rectovaginal swabs from 221 women at labor in four Lisbon hospitals were collected for GBS screening according to the CDC guidelines. Results: The PPV was 24.4%. IAP was administered to 100% of prenatally GBS positive women. There was no case of early onset GBS disease (EOD). Conclusions: Poor accuracy of prenatal cultures in identifying true candidates for IAP highlights the need for Portuguese clinical and laboratory guidelines to prevent EOD and antibiotic overtreatment of pregnant women.