Cervical Pessary Compared With Vaginal Progesterone for Preventing Early Preterm Birth: A Randomized Controlled Trial

To compare the effectiveness of a cervical pessary and vaginal progesterone to prevent spontaneous preterm births in pregnant women with cervical lengths 25 mm or less as measured by transvaginal ultrasonography.

This was a multicenter, open-label, randomized, noninferiority trial. Women with singleton pregnancies and a short cervix (25 mm or less) measured transvaginally at the second-trimester ultrasonogram were invited to participate. They were computer-randomized (one to one) into cervical pessary placement or treatment with vaginal progesterone (200 mg/24 hours). The primary outcome was spontaneous preterm delivery before 34 weeks of gestation. The noninferiority margin was set at 4% with a 0.025 one-sided α level and a statistical power of 80%. That is, if the 95% CI upper bound exceeded 4%, the pessary could not be deemed noninferior. A sample size of 254 women was required to show noninferiority of the pessary to progesterone.

The trial was conducted from August 2012 to April 2016 with the participation of 27 Spanish hospitals. A total of 254 patients were enrolled and 246 included in the intention-to-treat analysis. Demographic and baseline characteristics were similar across groups. The rate of spontaneous delivery before 34 weeks of gestation was 14% (n=18/127) in the pessary group and 14% (n=17/119) in the progesterone group with a risk difference of -0.11% (95% CI -8.85% to 8.62%; P=.99), that is, noninferiority was not shown for the pessary. The incidence of increased vaginal discharge (87% vs 71%, P=.002) and discomfort (27% vs 3%, P<.001) was significantly higher in the pessary group.

A cervical pessary was not noninferior to vaginal progesterone for preventing spontaneous birth before 34 weeks of gestation in pregnant women with short cervixes.

EU Clinical Trials Register, 2012-000241-13; ClinicalTrials.gov, NCT01643980.