Background According to CDC guidelines, prolonged rupture of membranes (PROM) mandates maternal intrapartum antimicrobial prophylaxis (IAP) for GBS whenever maternal GBS status is unknown. We aimed at assessing the local incidence, early detection and outcome of early-onset GBS sepsis (EOGBSS) in near term/term neonates born after PROM to women with unknown maternal GBS status with no IAP.

Methods During one year, we studied all neonates born beyond 35 weeks’ gestation with maternal PROM ⩾18 hrs, unknown maternal GBS status without prior administration of IAP. CBC, CRP, blood culture and PCR-amplification of bacterial 16S rRNA gene were performed in blood samples collected immediately after birth. Unfavorable outcome was defined by one or more of the following: GBS bacteremia, clinical signs of sepsis or positive PCR.

Results The study group included 212/3616 (5.9%) of the live-born neonates who met the inclusion criteria. Only 12 (5.7%) of these neonates presented signs suggestive of sepsis. PCR was negative in all cases. Fifty-eight neonates (27.4%) had CRP>1.0 mg/dL and/or CBC abnormalities, however, these were not significantly associated with unfavorable outcome. EOGBSS occurred in one neonate in this high-risk group (1/212 = 0.47%; 95% CI: 0.012 to 2.6).

Conclusions In sepsis-prone neonates born after PROM ⩾18 hrs with maternal unknown GBS status with no IAP, the incidence of EOGBSS is 10-fold higher than in the general Israeli neonatal population. In this regard, PCR has a role by virtue of its high negative predictive value. The high EOGBSS rate suggests developing local guidelines for management of these high-risk neonates.