Association between intracervical Foley balloon and clinical chorioamnionitis among patients with group B streptococcus colonization undergoing induction with standardized labor management

BACKGROUND Intracervical Foley balloons are commonly used for cervical ripening, but there has been a historical concern regarding an increased risk of clinical chorioamnionitis with Foley balloon use in patients with group B streptococcus. OBJECTIVE This study aimed to determine whether intracervical Foley balloon use in patients with group B streptococcus is associated with an increased risk of clinical chorioamnionitis. STUDY DESIGN This was a secondary analysis of a randomized controlled trial Mechanical and Pharmacologic Methods of Labor Induction: A Randomized Controlled Trial that compared cervical ripening agents within a standardized labor protocol. Foley balloon (alone, with oxytocin, or with misoprostol) was compared with misoprostol only to evaluate the primary outcome of clinical chorioamnionitis, defined based on the American College of Obstetricians and Gynecologists guidelines. Patients with a term, singleton pregnancy with intact membranes and an unfavorable cervix (Bishop score of ≤6 and dilation ≤2 cm) and a known group B streptococcus status were included. The secondary outcomes included a composite postpartum maternal infectious outcome consisting of any occurrence of endometritis, wound infection, postpartum urinary tract infection, or maternal sepsis; additional secondary outcomes included neonatal outcomes. Binomial regression with robust error variance was used to evaluate whether group B streptococcus status modified the relationship between Foley balloon use and clinical chorioamnionitis and to adjust for confounders. RESULTS A total of 491 patients were enrolled in the original trial. Of these patients, 467 had a known group B streptococcus status and underwent cervical ripening: 182 (39.0%) had group B streptococcus, and 285 (61.0%) did not have group B streptococcus. Moreover, 73.0% of patients received a Foley balloon, and 27.0% of patients did not receive a Foley balloon. There was no difference in the demographic or clinical characteristics between groups. The overall rate of clinical chorioamnionitis was 12.2%, with no difference between those with and without a Foley balloon (12.6% vs 11.1%, respectively; P=.66). Group B streptococcus status did not modify the association between Foley balloon use and clinical chorioamnionitis (relative risk, 0.93; 95% confidence interval, 0.50–1.72). This remained unchanged after adjusting for gestational age (adjusted relative risk, 0.87; 95% confidence interval, 0.45–1.67). Furthermore, other maternal and neonatal outcomes were similar between groups. CONCLUSION In this secondary analysis of a large randomized trial using a standardized labor protocol, there was no increased risk of infectious morbidity with Foley balloon use in patients overall and in patients with group B streptococcus. Our findings support that a Foley balloon can be safely used for cervical ripening in patients with group B streptococcus colonization. Intracervical Foley balloons are commonly used for cervical ripening, but there has been a historical concern regarding an increased risk of clinical chorioamnionitis with Foley balloon use in patients with group B streptococcus. This study aimed to determine whether intracervical Foley balloon use in patients with group B streptococcus is associated with an increased risk of clinical chorioamnionitis. This was a secondary analysis of a randomized controlled trial Mechanical and Pharmacologic Methods of Labor Induction: A Randomized Controlled Trial that compared cervical ripening agents within a standardized labor protocol. Foley balloon (alone, with oxytocin, or with misoprostol) was compared with misoprostol only to evaluate the primary outcome of clinical chorioamnionitis, defined based on the American College of Obstetricians and Gynecologists guidelines. Patients with a term, singleton pregnancy with intact membranes and an unfavorable cervix (Bishop score of ≤6 and dilation ≤2 cm) and a known group B streptococcus status were included. The secondary outcomes included a composite postpartum maternal infectious outcome consisting of any occurrence of endometritis, wound infection, postpartum urinary tract infection, or maternal sepsis; additional secondary outcomes included neonatal outcomes. Binomial regression with robust error variance was used to evaluate whether group B streptococcus status modified the relationship between Foley balloon use and clinical chorioamnionitis and to adjust for confounders. A total of 491 patients were enrolled in the original trial. Of these patients, 467 had a known group B streptococcus status and underwent cervical ripening: 182 (39.0%) had group B streptococcus, and 285 (61.0%) did not have group B streptococcus. Moreover, 73.0% of patients received a Foley balloon, and 27.0% of patients did not receive a Foley balloon. There was no difference in the demographic or clinical characteristics between groups. The overall rate of clinical chorioamnionitis was 12.2%, with no difference between those with and without a Foley balloon (12.6% vs 11.1%, respectively; P=.66). Group B streptococcus status did not modify the association between Foley balloon use and clinical chorioamnionitis (relative risk, 0.93; 95% confidence interval, 0.50–1.72). This remained unchanged after adjusting for gestational age (adjusted relative risk, 0.87; 95% confidence interval, 0.45–1.67). Furthermore, other maternal and neonatal outcomes were similar between groups. In this secondary analysis of a large randomized trial using a standardized labor protocol, there was no increased risk of infectious morbidity with Foley balloon use in patients overall and in patients with group B streptococcus. Our findings support that a Foley balloon can be safely used for cervical ripening in patients with group B streptococcus colonization.