Vancomycin Concentrations in Umbilical Cord Blood After Intrapartum Exposure

( Obstet Gynecol . 2025;145:435–438 DOI: 10.1097/AOG.0000000000005843) A study investigated the presence of vancomycin (VANC) in umbilical cord blood following maternal intrapartum administration using current weight-based dosing guidelines for group B Streptococcus (GBS) prophylaxis. The objective was to assess whether these concentrations reached or surpassed the established minimum inhibitory concentration (MIC) needed to prevent neonatal GBS infection. Moreover, GBS colonization affects nearly 30% of pregnant individuals in the United States, and standard intrapartum antibiotic prophylaxis (IAP) involves beta-lactam antibiotics such as penicillin or ampicillin. However, for those with severe beta-lactam allergies and clindamycin-resistant GBS strains, weight-based VANC is recommended. Unlike beta-lactams, VANC transfers less efficiently through the placenta and is rapidly cleared during pregnancy due to increased kidney filtration. Concerns persist about whether VANC reaches effective fetal concentrations. Existing guidelines from the American Academy of Pediatrics suggest VANC is insufficient for GBS IAP, and data on fetal exposure using updated dosing remains limited.