43: Effect of obesity on maternal and neonatal penicillin levels in women with Group B Streptococcus

Abstract

Early onset Group B Streptococcal (EOGBS) disease is the leading cause of early onset neonatal sepsis in the United States. Despite intrapartum penicillin (PCN) prophylaxis, infants of obese women are at 70-80% increased risk of developing EOGBS disease compared to infants of non-obese women. Our objective was to determine whether the recommended PCN dosing achieves adequate PCN levels in obese women and their neonates. We performed a prospective cohort study from Feb 2018-Jan 2019 of term GBS positive women (by rectovaginal swab at 35-37 weeks) receiving PCN. The following outcomes were compared between obese women (BMI ≥35 kg/m2) and non-obese women (BMI ≤30 kg/m2): vaginal GBS colonization at admission and after 2 completed PCN doses, serum PCN concentration in maternal blood (after 2 completed PCN doses), umbilical cord blood PCN levels, and neonatal GBS colonization (via postnatal ear swab). Fifty-six women were needed to detect a 0.75 standard deviation difference in cord blood PCN levels. 56 women were enrolled and had all specimens collected; 51 had complete data for analysis (non-obese n=26, obese n=25). Approximately 40% of women were GBS negative on admission with no difference between groups (61% vs. 62%, p=0.96). There was no difference in the median maternal serum PCN levels between groups (Table 1). There was, however, a significant difference in median cord blood PCN levels between groups (6.7 mcg/mL vs. 2.7 mcg/mL, p< 0.001) with no difference in time from PCN to delivery. Postnatally, 8% of neonates born to women in both groups were GBS positive by ear swab with no difference between groups. There were no differences in infectious outcomes. Whether the 2.5 times lower median cord blood PCN levels in obese women affects rates of EOGBS disease requires future study. Importantly, our study demonstrates that current practices for EOGBS disease prevention result in unnecessary exposure in up to 40% of patients. These findings demand improved strategies to mitigate the risks of excess antibiotic usage while optimizing prevention of EOGBS infection.View Large Image Figure ViewerDownload Hi-res image Download (PPT)