Vaginal Group B Streptococcal Colonization Not Associated With Chorioamnionitis In Laboring Patients

Abstract

Multiple studies have reported increased rates of chorioamnionitis associated with group B streptococcal (GBS) colonization. We sought to estimate the risk of chorioamnionitis associated with GBS positive status in term laboring patients. This is a retrospective cohort study of term (≥37 weeks), singleton pregnancies who labored at our tertiary care center from 2005 to 2018. The primary outcome of chorioamnionitis was defined as maternal intrapartum fever (single oral temperature of >39°C or 38–38.9°C for 30 minutes) and one or more of the following: maternal leukocytosis, purulent cervical drainage, or fetal tachycardia. The primary exposure was GBS colonization in the medical record. Cox proportional hazard regression was used to model the effect of GBS on the risk of chorioamnionitis while adjusting for number of cervical exams, epidural use, meconium, smoking, parity, BMI, duration of rupture, labor induction and cesarean section. 19,688 individuals met inclusion criteria and 981 (5%) patients met criteria for clinical chorioamnionitis. Of the subjects diagnosed with chorioamnionitis, 188 (19.2%) were GBS positive compared to 25.2% in those not diagnosed with infection (p < 0.001). GBS colonization was not associated with an increased rate of chorioamnionitis after adjusting for potential confounders (hazard ratio [HR] 0.6, 95% confidence interval [CI] 0.5-0.7; p= < 0.001). GBS colonization rates were higher among patients undergoing unplanned cesarean delivery (Vaginal: 12.0% vs Cesarean: 13.4%, p=0.01). Meconium rates were similar between the two groups (GBS positive: 19.0% vs GBS negative: 19.4%, p=0.06). In contrast to previous reports, GBS colonization in laboring patient did not increase the risk of chorioamnionitis. Individuals with positive GBS status should not be counseled on increased risk of chorioamnionitis.