Antepartum Screening and Non-selective Intrapartum Chemoprophylaxis for Group B Streptococcus

Summary: The efficacy of antibiotic chemoprophylaxis in labour for all maternal carriers of Group B streptococcus with respect to the neonatal mortality and morbidity was analyzed. The intervention consisted of a policy of maternal screening for Group B streptococcus at 28 weeks' gestation by a low vaginal swab, cultured on to nonselective media. If positive, all carriers were treated with intrapartum ampicillin regardless of other obstetric risk factors. The main outcome measures were studied prospectively for 16 months before and for 32 months after instituting the intervention. These included the incidence of early-onset Group B streptococcal infection as defined by either a blood culture or a symptomatic neonate with a positive urinary streptococcal antigen test, the mortality and the morbidity.
Intrapartum ampicillin significantly reduced the incidence of early-onset Group B streptococcal disease, from 2.0 to 0.37 per 1,000 livebirths for neonates with a positive blood culture (p < 0.03), and from 4.9 to 1.5 per 1,000 livebirths for symptomatic infants with a positive urinary antigen test (p < 0.004) and the attributable morbidity, namely, neonates who were: admitted to a level 2 or 3 unit (p < 0.004); treated with antibiotics (p < 0.004); preterm (p < 0.04); ventilated (p < 0.01). Seventy five per cent of the maternal population was overall actually screened and the carriage rate was 12%. No serious adverse reactions to ampicillin were observed.
Significant reduction in early-onset neonatal Group B streptococcal disease has occurred concurrent with antepartum screening and nonselective intrapartum chemoprophylaxis.