A Population-Based Comparison of Strategies to Prevent Early-Onset Group B Streptococcal Disease in Neonates

Abstract

In 1996 the American College of Obstetricians and Gynecologists, along with the American Academy of Pediatrics and the Centers for Disease Control and Prevention, recommended one of two courses for healthcare providers toidentify women who should receive intrapartum antibiotic prophylaxis to prevent group B streptococcal (GBS) disease in infants aged 1 week or less: screening by culture or assessment of clinical risk factors. These two approaches have now been compared in a retrospective cohort study of approximately 630,000 live births. Study cases were accessed in the years 1998-1999 in eight geographic areas of the United States where active surveillance for GBS infection was under way. A random sample of these areas yielded 5144 births. The 312 cases of early onset GBS disease translated into an overall incidence of 0.5 case per 1000 live births. No clinical risk factors for transmitting GBS disease were identified in 62% of cases. More than half of the women in the overall population (52%) were screened before delivery. On univariate analysis, prenatal culture screening correlated with a lower risk of early onset GBS disease than was the clinical risk-based approach; the relative risk (RR) was 0.48. The most prominent risk factors were a previous infant having GBS disease and intrapartum fever. GBS bacteriuria during pregnancy was not a factor, but more than 80% of all women with bacteriuria received intrapartum antibiotics. Screening continued to be associated with a reduced risk on multivariate analysis (RR, 0.46). Screening protected full-term infants when analyzed separately. Intrapartum antibiotic treatment was 89% effective in preventing early onset GBS disease in culture-positive women. It was estimated that, assuming perfect implementation of either strategy, intrapartum antibiotics would be used in 31% of screened women and 29% of those having risk-based assessment. These findings suggest that it makes sense to further consider a recommendation favoring universal screening to prevent GBS disease in newborn infants.