Background: Recognition that ascending infection leads to preterm birth has led to a number of studies that have evaluated the treatment of vaginal infections in pregnancy to reduce preterm birth rates. However, the role of candidiasis is relatively unexplored. Our aim was to undertake a systematic review and meta-analysis to assess whether treatment of pregnant women with vulvovaginal candidiasis reduces preterm birth rates and other adverse birth outcomes.

Methods: We undertook a systematic review and meta-analysis of published randomised controlled trials (RCTs) in which pregnant women were treated for vulvovaginal candidiasis (compared to placebo or no treatment) and where preterm birth was reported as an outcome. Trials were identified by searching the Cochrane Central Register of Controlled Trials, Medline and Embase databases to January 2014. Trial eligibility and outcomes were pre-specified. Two reviewers independently assessed the studies against the agreed criteria and extracted relevant data using a standard data extraction form. Meta-analysis was used to calculate pooled rate ratios (RR) and 95% confidence intervals (CI) using a fixed-effects model.

Results: There were two eligible RCTs both among women with asymptomatic candidiasis, with a total of 685 women randomised. Both trials compared treatment with usual care (no screening for, or treatment of, asymptomatic candidiasis). Data from one trial involved a post-hoc subgroup analysis (n = 586) of a larger trial of treatment of 4,429 women with asymptomatic infections in pregnancy and the other was a pilot study (n = 99). There was a significant reduction in spontaneous preterm births in treated compared with untreated women (meta-analysis RR = 0.36, 95% CI = 0.17 to 0.75). Other outcomes were reported by one or neither trial.

Conclusions: This systematic review found two trials comparing the treatment of asymptomatic vaginal candidiasis in pregnancy for the outcome of preterm birth. Although the effect estimate suggests that treatment of asymptomatic candidiasis may reduce the risk of preterm birth, the result needs to be interpreted with caution as the primary driver for the pooled estimate comes from a post-hoc (unplanned) subgroup analysis. A prospective trial with sufficient power to answer the clinical question 'does treatment of asymptomatic candidiasis in early pregnancy prevent preterm birth' is warranted.

Systematic review registration: PROSPERO CRD42014009241.