Eight-Year Outcome of Universal Screening and Intrapartum Antibiotics for Maternal Group B Streptococcal Carriers

Abstract

Objectives. To report the outcome of intervention to reduce early-onset group B streptococcal disease (EOGBSD) at a tertiary maternity hospital in Sydney and to review all cases of EOGBSD since intervention to improve outcomes further. Methodology. A prospective study was made of all cases of EOGBSD in the 16 months before and 8 years after an intervention that comprised universal screening and intrapartum ampicillin for all maternal carriers of group B streptococcus. Carriers were detected by screening all women at 28 weeks, or 24 weeks with known risk factors for preterm birth, by low vaginal swab, cultured onto blood agar and treated with intravenous ampicillin in labor, 1 g every 6 hours until delivery. Women with a routine midstream urine test positive for group B streptococcus, a previous neonate with EOGBSD, or preterm labor with an unknown carrier status were also treated. EOGBSD was detected by screening all neonates with maternal and/or neonatal risk factors for sepsis. Results. The incidence of blood culture-positive EOGBSD for all live births before intervention was 1.4 per 1000 compared with a rate after intervention of 0.2 per 1000 live births. The incidence, if there were clinical signs of infection and the urine tested positive for streptococcal antigen, decreased from 3.5 per 1000 before intervention to 0.6 per 1000 live births. There was a statistically significant reduction in neonatal morbidity outcomes after intervention, including requirement for admission and treatment in a neonatal unit and the need for ventilation. An audit indicated that by the 8th year, 90% of all pregnant women were screened by a low vaginal swab at 28 weeks and 10.5% were carriers. After intervention, of the 28 neonates with EOGBSD, 64% were associated with departure from the protocol. Conclusion. The intervention has coincided with a significant decrease in the incidence of blood culture-positive EOGBSD to 0.2 and urine streptococcal antigen-positive disease to 0.6 per 1000 live births. The 84% reduction in EOGBSD has been obtained by treating 244 neonates in labor to prevent disease in one neonate. Additional reduction seems possible by improving the compliance by staff with the protocol. By contrast, before intervention and in maternity units throughout Australia with no intervention, the rates for EOGBSD remain largely unchanged at ∼2 per 1000 live births.