Preventing group B Streptococcus neonatal disease with intrapartum prophylaxis: a retrospective study to detect its use in case of unknown colonization status

BACKGROUND: Group B Streptococcus (GBS) is the leading cause of neonatal morbidity and mortality in developed countries. This study aims primarily to estimate the prevalence of maternal GBS positivity and secondarily to evaluate the compliance and the effectiveness of the current GBS prevention protocol. METHODS: This retrospective study has considered 27382 single pregnancies carried to delivery between 2001 and 2014 at our Obstetrics and Gynecology clinic. All women carrying a singleton pregnancy in the considered period were eligible to be included in this study. RESULTS: The GBS swab was positive in 17.66% of cases, negative in 51.93%, and unknown in 30.41%. Data collected revealed that out of the total of GBS-positive women, 3362 were treated with antibiotic prophylaxis, and 1331 were not. There were no differences between cases admitted to Neonatal Intensive Care Unit and perinatal deaths between treated and non-treated GBS-positive pregnancies. Moreover, the data showed that 74.62% of patients between 34 and 37 weeks of gestation at the time of delivery were treated with antibiotic prophylaxis unnecessarily, and 25.38% of patients >37 weeks of gestation whose GBS status at delivery was unknown would have required intrapartum antibiotic prophylaxis. The only risk factor for chorioamnionitis among GBS-positive women in multivariate logistic regression analysis was an early gestational age (OR 0.61; 95% CI: 0.56-0.66; P<0.05). CONCLUSIONS: GBS prevalence was found to be 17.66%, and prophylaxis in colonized patients was carried out correctly according to our internal procedure allowing a low incidence of adverse outcomes. Finally, the only risk factor associated with chorioamnionitis in GBS patients was early gestational age at delivery.