IntroductionThis study aimed to investigate the incidence of neonatal early-onset group B streptococcal (GBS) infection in Sweden after promulgation of guidelines (2008) for risk factor-based intrapartum antibiotic prophylaxis, and evaluate the presence of risk factors and obstetric management in mothers. Material and methodsNational registers were searched for infants with early-onset GBS infection during 2006-2011. Medical records of cases and case mothers were abstracted. Verified cases of sepsis/meningitis and cases with clinical sepsis/pneumonia were documented, as well as risk factors in case mothers and timeliness of intrapartum antibiotic prophylaxis administration. ResultsThere were 227 cases with verified infection, with an incidence of 0.34 of live births during the whole period. There was a significant decrease after promulgation of guidelines, from 0.40 to 0.30 parts per thousand [odds ratio (OR) 0.75, 95% confidence interval (CI) 0.57-0.99]. A significant decrease in the number of cases with clinical GBS sepsis/pneumonia was also observed. In parturients with one or more risk factors, the incidence of any GBS infection was reduced by approximately 50% (OR 0.47, 95% CI 0.35-0.64), although there were many cases where the opportunity for timely administration of intrapartum antibiotic prophylaxis was missed. In infants of mothers without risk factor(s) there was no reduction in early-onset GBS morbidity. The mortality in verified cases was 4.8% (95% CI 2.1-7.6). ConclusionsThe introduction of national guidelines for risk-based intrapartum antibiotic prophylaxis coincided with a significant 50% risk reduction of neonatal early-onset GBS infection in infants of parturients presenting with one or more risk factors. A stricter adherence to guidelines could probably have reduced the infant morbidity further.