Intrapartum antibiotics for known maternal Group B streptococcal colonization

Maternal colonization with group B streptococcus (GBS) during pregnancy increases the risk of neonatal infection by vertical transmission. Administration of intrapartum antibiotic prophylaxis (IAP) during labor has been associated with a reduction in early onset GBS disease (EOGBSD). However, treating all colonized women during labor exposes a large number of women and infants to possible adverse effects without benefit.

To assess the effect of IAP for maternal GBS colonization on neonatal: 1) all cause mortality and 2) morbidity from proven and probable EOGBSD, late onset GBS disease (LOD), maternal infectious outcomes and allergic reactions to antibiotics.

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2009).

Randomized trials assessing the impact of maternal IAP on neonatal GBS infections were included.

We independently assessed eligibility and quality of the studies.

Three trials (involving 852 women) evaluating the effects of IAP versus no treatment were included. The risk of bias was high. The use of IAP did not significantly reduce the incidence of all cause mortality, mortality from GBS infection or from infections caused by bacteria other than GBS. The incidence of early GBS infection was reduced with IAP compared to no treatment (risk ratio 0.17, 95% confidence interval (CI) 0.04 to 0.74, three trials, 488 infants; risk difference -0.04, 95% CI -0.07 to -0.01; number needed to treat to benefit 25, 95% CI 14 to 100, I(2) 0%). The incidence of LOD or sepsis from organisms other than GBS and puerperal infection was not significantly different between groups.One trial (involving 352 women) compared intrapartum ampicillin versus penicillin and reported no significant difference in neonatal or maternal outcomes.

Intrapartum antibiotic prophylaxis appeared to reduce EOGBSD, but this result may well be a result of bias as we found a high risk of bias for one or more key domains in the study methodology and execution. There is lack of evidence from well designed and conducted trials to recommend IAP to reduce neonatal EOGBSD.Ideally the effectiveness of IAP to reduce neonatal GBS infections should be studied in adequately sized double-blind controlled trials. The opportunity to conduct such trials has likely been lost, as practice guidelines (albeit without good evidence) have been introduced in many jurisdictions.