Intrapartum antibiotic prophylaxis for Group B Streptococcus (GBS) reduces rates of clinical chorioamnionitis and peripartum infectious morbidity in patients receiving induction with protocolized labor management, according to a recent study published in The American Journal of Obstetrics & Gynecology.
Takeaways
- The study suggests that administering intrapartum antibiotic prophylaxis to GBS-positive pregnant individuals undergoing induction of labor significantly reduces the rates of clinical chorioamnionitis and peripartum infectious morbidity.
- Rectovaginal colonization with GBS during pregnancy is identified as a leading cause of early onset neonatal sepsis, affecting over one-third of neonates presenting with this condition. GBS infection can develop in up to 1% of neonates born to GBS-colonized mothers without antibiotic prophylaxis.
- Clinical chorioamnionitis, described as an infection affecting various components of pregnancy, occurs in 2% to 12% of term deliveries. GBS colonization is identified as a risk factor for clinical chorioamnionitis, emphasizing the importance of understanding the impact of intrapartum antibiotic prophylaxis on this risk.
- The study findings reveal a 49% reduced rate of clinical chorioamnionitis in GBS-positive patients who received intrapartum antibiotic prophylaxis compared to GBS-negative patients. Additionally, the odds of peripartum infectious morbidity were lower in the GBS-positive group.
- The study's conclusion raises the question of whether tailored intrapartum antibiotic prophylaxis, based on factors beyond GBS positivity, could be considered to prevent chorioamnionitis. This suggests the need for further exploration of personalized approaches to intrapartum antibiotic prophylaxis in specific cases.
Rectovaginal (RV) colonization with GBS during pregnancy has been reported as the leading cause of early onset neonatal sepsis. Of the approximately 1 in 1000 neonates who present with early onset neonatal sepsis, over one-third are because of GBS.
A clinically significant GBS infection will develop in up to 1% of neonates born to GBS colonized mothers without an intrapartum antibiotic prophylaxis. Since 1996, the Centers for Disease Control and Prevention (CDC) has recommended intrapartum antibiotic prophylaxis against GBS to reduce early onset neonatal sepsis risk. However, there is little data on how this practice impacts clinical chorioamnionitis and other conditions.
Clinical chorioamnionitis, described by study authors as, “an infection of the amniotic fluid, placenta, fetus, membranes, or decidua,” impacts 2% to 12% of term deliveries. GBS colonization is a known risk factor of clinical chorioamnionitis, making it important to understand the impact of intrapartum antibiotic prophylaxis for GBS on clinical chorioamnionitis risk.
To assess the association between GBS colonization, intrapartum antibiotic prophylaxis, and clinical chorioamnionitis, investigators conducted an exploratory secondary analysis of a large, randomized trial. The original trial included patients aged 18 years and older with a full-term induction of labor between May 2013 and June 2015.
Participants had a singleton gestation in cephalic presentation, intact membranes, and an unfavorable cervix. Exclusion criteria included previous cesarean delivery, contraindication to vaginal delivery, not speaking English, and having HELLP syndrome, HIV, eclampsia, or severe fetal growth restriction with abnormal umbilical artery dopplers.
Patients in the trial were randomized to receive Foley alone, misoprostol alone, misoprostol plus Foley balloon, or oxytocin plus Foley balloon. All patients with a known GBS status were included in the secondary analysis, receiving third trimester GBS screening.
Intrapartum antibiotic prophylaxis was given to patients with GBS from the beginning of induction through delivery. This care was given as “penicillin 5 million units intravenous (IV), followed by 3 million units IV every 4 hours until delivery,” according to study authors.
A clinical chorioamnionitis diagnosis was the primary outcome of the analysis. Diagnoses were determined by a maternal temperature above 39.0°C or persisting oral temperature of 38°C to 38.9°C. This outcome was compared between GBS positive patients receiving intrapartum antibiotic prophylaxis and GBS negative patients not receiving intrapartum antibiotic prophylaxis.
Secondary outcomes included postpartum endometriosis, maternal sepsis, abdominal wound separation or infection, and composite of any maternal peripartum infectious morbidity. Neonatal outcomes included neonatal sepsis, 1- and 5-minute Apgar scores, neonatal intensive care unit(NICU) admission, severe respiratory stress, length of stay, and composite neonatal morbidity.
There were 466 individuals included in the final analysis, 37.3% of whom were GBS positive and received intrapartum antibiotic prophylaxis and 62.7% of whom were GBS negative and did not receive intrapartum antibiotic prophylaxis. Of patients with GBS positivity, GBS was diagnosed by RV culture in 75.9%, GBS bacteriuria in 20.7%, and prior history in 3.4%.
A cervical Foley balloon was placed in 72.1% of patients, and the average gestational age at induction was 39 weeks. A cesarean delivery was reported in 26.6% of patients overall, with rates similar between groups. A median 4 doses of antibiotic were given to patients in the GBS positive group.
GBS positive patients receiving intrapartum antibiotic prophylaxis had a 49% reduced rate of clinical chorioamnionitis compared to GBS negative patients, at 8.1% vs 14.7%, respectively. The odds of being diagnosed with any peripartum infectious morbidity were also decreased in GBS patients receiving treatment vs GBS negative patients, at 8.1% vs 15.8%, respectively.
A wound infection was observed in 4 patients in the GBS negative group vs 1 patient in the GBS positive group. NICU admission was significantly less likely in the GBS positive group than the GBS negative group, at 3.4% vs 15.1%, respectively.
These results indicated an association between intrapartum antibiotic prophylaxis for GBS and peripartum infectious morbidity. Investigators concluded these findings question whether tailored intrapartum antibiotic prophylaxis could be used to prevent chorioamnionitis in cases other than GBS positivity.
Reference
McCoy JA, Bromwich K, Gerson KD, et al. Association between intrapartum antibiotic prophylaxis for Group B Streptococcus colonization and clinical chorioamnionitis among patients undergoing induction of labor at term. Am J Obstet Gynecol. 2023;229:672.e1-8. doi:10.1016/j.ajog.2023.06.038
