The recurrence risk of group B Streptococcus in consecutive deliveries

Background: Group B streptococcus (GBS) is a significant cause of neonatal morbidity and mortality. GBS maternal colonization status was found to be transient, intermittent, or chronic and screening during each subsequent pregnancy was advised. Recent studies showed that GBS colonization rate was higher among women with history of GBS positive in prior pregnancy.Objective: To establish the cumulative risk of group B streptococcus (GBS) colonization in consecutive subsequent term deliveries as referred to the first delivery GBS colonization status.Study design: A retrospective cohort study, based on a validated computerized database at a tertiary single center between the years 2005-2016. Pregnant women preform vaginal-rectal culture at 35-37 weeks of gestation. We analyzed records of term primiparas women that had records of up to three additional term consecutive deliveries and GBS colonization status.Results: 8641 primiparas met inclusion criteria; 3972 (46.0%), 993 (11.5%), and 243 (2.8%) had second, third, and fourth consecutive deliveries with recorded GBS status respectively. The overall colonization rate for primiparas was 28.4%. The cumulative rates and cumulative risks of repeated GBS positive colonization at the second, third and fourth term consecutive deliveries were 62.0%, 6.93 (95% CI 5.96-8.06), 68.0%, 5.05 (95% CI, 3.67-6.93), and 66.1%, 2.96 (95% CI, 1.54-5.68), respectively. Notably, after a negative GBS colonization in the first, second, and third repeated deliveries, the rate and cumulative risk of GBS positive in each consecutive delivery was significantly lower: 18.2%, 0.14, (95% CI 0.12-0.17), 19.4%, 0.21 (95% CI 0.15-0.28), and 21%, 0.26 (95% CI 0.13-0.51) for the second, third, and fourth consecutive deliveries, respectively.Conclusion: GBS colonization status at the time of first pregnancy is a milestone for the colonization risk in subsequent term deliveries. This risk evaluation may influence the decision-making process for future screening and intrapartum antibiotic prophylaxis for term consecutive deliveries.