Objective: To determine the incidence of early-onset group B beta hemolytic streptococcal (EOGBS) infection and the association between changes in the incidence and intrapartum antibiotic prophylaxis (IAP).
Study design: A retrospective population survey of infants with GBS at < 7 days of age with a nested case-control study of non-GBS infants over the same time period, January 1985 to December 1998. The incidence of GBS and maternal antibiotic treatment during labor was analyzed as a function of time period: prior to publication of guidelines for prevention of EOGBS (1985-1992), following AAP/ACOG guidelines (1993-1995), and following CDC consensus guidelines (1996-1998).
Results: Fifty-six cases of EOGBS infection occurred among 53,088 live births. The incidence declined from 1.5/1000 before any guidelines to 0.67/1000 after AAP/ACOG guidelines (p = 0.004), and continued to decline after the CDC consensus statement (0.28/1000) (p = 0.38). IAP remained stable (33% of at risk mothers) until after introduction of the CDC consensus guidelines (59%, p = 0.02).
Conclusion: IAP did not fully explain the decline in EOGBS incidence in our center.