A Randomized Controlled Trial

METHODS: In a multicenter open-label randomized controlled trial, a cervical pessary was compared with no intervention (control group) (one-to-one ratio). Women between 24 and 34 weeks of gestation at high risk for preterm birth based on a short cervical length (less than 15 mm) or an intermediate cervical length (between 15 and 30 mm) with a positive fetal fibronectin test who did not deliver after an episode of threatened preterm labor were eligible. The primary outcome was birth before 37 weeks of gestation. Secondary outcomes were a composite adverse neonatal outcome, preterm birth before 34 and 32 weeks of gestation, and side effects. A total sample size of 200 women carrying singletons was planned so as to have adequate statistical power to detect a reduction in the rate of preterm birth from 40% to 20%. Women with twin gestations were also enrolled but were considered only in secondary analyses. After a planned interim analysis, the trial was stopped for futility.