Risk factors for group B streptococcus early-onset disease: an Italian, area-based, case-control study.

Intrapartum antibiotic prophylaxis (IAP) prevents group B streptococcus (GBS) early-onset disease (EOD). No European study evaluates the relative impact of risk factors (RFs) for EOD after a screening-based strategy and widespread IAP use We aimed to evaluate the risks of EOD in an Italian region where a screening-based strategy for preventing EOD was implemented. Cases of EOD born at or above 35 weeks' gestation were reviewed and matched with controls. There were 109 cases of EOD among 532,154 live births. Most cases had negative GBS prenatal screening (56/91, 61.5%) and were unexposed to IAP (86/109, 78.9%). At multivariate analysis, GBS bacteriuria ( = 6.99), positive prenatal screening ( = 13.7) and maternal intrapartum fever ( = 188.3) were associated with an increased risk of EOD, whereas intrapartum beta-lactam antibiotics were associated with a decreased risk of EOD (≥4 h:  = 0.008; <4 h:  = 0.04). Neonates born to nonfebrile, GBS positive pregnant women, receiving beta-lactam antibiotics had very low probability of EOD, particularly if IAP was adequate. GBS positive prenatal screening, GBS bacteriuria and intrapartum fever are associated with EOD. Intrapartum beta-lactam antibiotics reduce the probability of EOD in neonates born to nonfebrile mothers.