Risk factors for early onset neonatal group B streptococcal sepsis: case-control study

Abstract

Objectives: To quantify risk factors for and the prevalence of early onset group B streptococcal sepsis in neonates in a geographically defined population.

Design: Cases were collected prospectively for two years from April 1998 and compared with four controls each, matched for time and place of delivery.

Setting: The former Northern health region of the United Kingdom.

Participants: Infants infected with group B streptococcus in the first week of life.

Results: The prevalence of early onset group B streptococcal sepsis was 0.57 per 1000 live births. Premature infants comprised 38% of all cases and 83% of the deaths. Prematurity (odds ratio 10.4, 95% confidence interval 3.9 to 27.6), rupture of the membranes more than 18 hours before delivery (25.8, 10.2 to 64.8), rupture of the membranes before the onset of labour (11.1, 4.8 to 25.9), and intrapartum fever (10.0, 2.4 to 40.8) were significant risk factors for infection. Had the interim recommendations on best practice issued by the Group B Streptococcus Working Group of the Public Health Laboratory Service been uniformly applied to the fetuses alive at the onset of labour, 29 of 37 (78%) might have been given antibiotic prophylaxis during labour. At least 23 of these 29 (79%) could have had antibiotics for four hours or more before delivery. To achieve this, 16% of all women would have been given antibiotics during labour.

Conclusions: Early onset group B streptococcal sepsis remains an important problem in the United Kingdom. Prevention based on risk factors might reduce the prevalence at the cost of treating many women with risk factors. Using rupture of the membranes before the onset of labour as a risk factor might be expected to improve the success of guidelines for prophylaxis.