Preventing early-onset group B streptococcal sepsis: is there a role for rescreening near term?

The Centers for Disease Control and Prevention 2010 guidelines recommend group B streptococcus (GBS) screening at 35-37-week gestation to identify women with positive cultures who should receive intrapartum antibiotics and notes that the predictive value of a negative culture declines after 5 weeks. However, despite the lack of evidence, current guidelines do not recommend rescreening for those screened between 35 and 37 weeks. Our objectives were to investigate the rate of conversion from negative to positive results in women rescreened after appropriate screening at 35-37-week gestation and to examine the impact of rescreening on the use of intrapartum antibiotics. Additionally, we examined cases of early-onset group B streptococcal sepsis (early-onset GBS) in term neonates. We performed a retrospective cohort study of women delivering liveborn infants 1 January, 2010-31 December, 2014 in Kaiser Permanente Northern California. Data were obtained from database extraction and chart review. We identified 135,585 women with GBS screening at 35-37-week gestation; 4511 (3.3%) women were rescreened. Of the 3860 (85.6%) initially screened negative, 218 (5.6%) converted to positive. Fewer women in the discordant negative to positive group received GBS prophylaxis prior to delivery compared with women with a single positive culture (65.9 versus 92.3%,  < .001). In the discordant negative to positive group, results were available at the time of delivery in 133 of 217 subjects (61.3%). There were 18 cases of early-onset GBS at term (0.10 per 1000 livebirths); the majority of cases occurred among women with negative screening. Our results provide support for the current CDC recommendation against rescreening near term for those women already screened at 35-37-week gestation given the low rate of conversion from negative to positive, and the extremely low rate of early-onset GBS in the screened population.