Prophylactic antibiotics for the prevention of preterm birth in women at risk: a meta-analysis

BACKGROUND: Preterm birth (PTB) is the major determinant of perinatal morbidity and mortality. Infection is implicated in a large proportion of preterm deliveries, but there is no consensus regarding the efficacy of antibiotic prophylaxis for women at risk. AIM: To determine whether antibiotic treatment reduces the risk of preterm delivery in asymptomatic pregnant women at risk of PTB. METHOD: Relevant publications were identified via electronic searches of MEDLINE (1966 to August 2005), The Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Central Register of Controlled Trials (the Cochrane Library, Issue 3, 2005) and PubMed using multiple search terms related to PTB and antibiotics. Publications were limited to randomised controlled trials comparing antibiotics with placebo given to asymptomatic non-labouring women. A random effect model was used, and combined risk ratios calculated for the various risk groups. Associations between treatment effect and the rate of PTB were analysed by meta-regression. RESULTS: Seventeen trials were included, 12 identifying women at risk by abnormal vaginal flora, three on women at high risk from a previous PTB and two recruiting women based on positive fetal fibronectin status. There was no significant association between antibiotic treatment and reduction in PTB irrespective of criteria used to assess risk, the antimicrobial agent administered, or gestational age at time of treatment (overall combined random effect for delivery at less than 37 weeks RR 1.03 (95% CI 0.86-1.24)). CONCLUSIONS: Treating women at risk of PTB with antibiotics does not reduce the risk of subsequent PTB.