Objective To identify the incidence of early-onset group B streptococcal infection and to describe the antecedent maternal risk factors, in order to provide data to inform the design of interventional strategies that could be introduced in the UK to reduce the burden of this infection.
Design A retrospective study with review of case notes of mothers and babies.
Setting Seven maternity units in London during 1990–1999.
Population All cases of proven early-onset neonatal group B streptococcal infection.
Methods Identification of presence of risk factors that could be used to select women for the offer of intrapartum antibiotic prophylaxis.
Main outcome measures Incidence and case-fatality rate of invasive early-onset group B infection.
Results One hundred and forty cases were identified among a birth cohort of 198,388 live births, an incidence of 0.71 per 1000 live births. Twenty-two babies died, a case-fatality rate of 15.6% or 1.1 per 100,000 live births. Women of black ethnic origin, and those who had had a previously affected infant, multiple pregnancy, preterm delivery, prolonged rupture of membranes or intrapartum fever all had a significantly increased risk of delivering an infected infant.
Conclusions These data suggest that the incidence of early-onset group B streptococcal infection in these London centres is sufficiently high to warrant administration of intrapartum antibiotics to at-risk women.