Effectiveness of cervical pessary in women with arrested preterm labor compared to those with asymptomatic cervical shortening

Objective: To determine whether the effectiveness of cervical pessary is different in women who experienced cervical shortening after a threatened preterm labor episode compared to those with asymptomatic short cervix. Methods: Retrospective study on singleton pregnancies at risk for preterm delivery (PTD) due to cervical length <25 mm before 28 weeks, who were treated with Arabin cervical pessary. Two groups of patients were compared: those who had contractions causing shortening of the cervix, prior to pessary placement, and those who had asymptomatic cervical shortening. Patients carrying a multiple pregnancy and those who underwent iatrogenic PTD were excluded. The primary outcome was the incidence of PTD at different gestational ages. Secondary outcome was the rate of preterm premature rupture of membrane (pPROM). The groups were compared using univariate and multivariate analyses. Results: 115 patients that met the inclusion criteria were identified. Of these, 91 (79%) had asymptomatic cervical shortening, while 24 (21%) had an episode of threatened preterm labor that resolved, and the pessary was placed after the contractions had stopped. The two groups were similar for maternal characteristics, obstetric history, mean gestational age and length of the cervix at the time of pessary insertion. The median gestational age at delivery was significantly lower (36.4 vs 38.0 weeks, p = .02), and the incidence of PTD significantly higher (58.3% vs 30.8%, OR 4.69, 95% CI 1.68-13.1, p < .01) among women who had arrested preterm labor before the pessary was placed compared to the asymptomatic group, after controlling for confounders. The incidence of PTD before 34 and before 32 weeks was also significantly higher in the symptomatic group (p = .02 and p = .005, respectively). Women with asymptomatic cervical shortening had a longer interval between the placement of the pessary and delivery (median 15 weeks). pPROM occurred with a similar incidence in both groups. Conclusions: Arabin cervical pessary to prevent preterm delivery seems be less effective in women with a short cervix following an episode of threatened preterm labor than in those with asymptomatic cervical shortening in the second trimester. This finding may help physicians to select patients in which cervical pessary is more likely to be effective, and to improve patient's counseling about this intervention.