Effectiveness of the cervical pessary for the prevention of preterm birth in singleton pregnancies with a short cervix: a meta-analysis of randomized trials

Objective: To assess the efficacy of cervical pessary application for the prevention of spontaneous preterm birth (SPB) in singleton pregnancies with a sonographically measured short cervix. Methods: Searches were conducted in PubMed-Medline, Embase, Scopus, Web of Science, and Cochrane Library, and clinical trial registries for randomized controlled trials (RCTs) published in all languages from inception through 28 July 2018. Inclusion criteria were registered RCTs of singleton pregnants with a short cervix (≤ 25 mm) measured at 22–24 weeks comparing the use of a cervical pessary versus controls over the risk of SPB. Risk of bias was evaluated with the Cochrane tool. Risk ratios (RRs) and mean differences and 95% confidence intervals (CIs) were calculated. Results: We identified three RCTs meeting defined inclusion criteria, including a total of 1612 pregnancies (805 used a cervical pessary). SPB risk at < 37 was lower for participants using the pessary (RR 0.46; 95% CI 0.28–0.77). Pessary application was associated with a higher risk of presenting vaginal discharge (RR 2.05; 95% CI 1.82–2.31). There were no significant differences between pessary users and controls in terms of SPB at < 28 and < 34 weeks, and for any type of preterm birth < 34 weeks; mean gestational age and infant weight at delivery; and the risks of chorioamnionitis, cesarean delivery, and perinatal or neonatal outcomes. Sub-analysis by risk of bias showed that there was a lower risk of SPB < 34 weeks (RR 0.33; 95% CI 0.16–0.66) in two RCTs with low risk of bias. Conclusion: Cervical pessary application was associated with a reduced risk of SPB at < 37 weeks and a higher risk of vaginal discharge.