Cerclage for Short Cervix ≤20mm before 24 weeks in Singleton Gestations without Prior Spontaneous Preterm Birth Decreases Preterm Birth: a Meta-analysis of Randomized Controlled Trials using Individual Patient-level Data

Objective: To evaluate the efficacy of cervical cerclage in preventing preterm birth (PTB) in asymptomatic singleton pregnancies without prior spontaneous PTB and with a mid-trimester short transvaginal ultrasound cervical length (TVU CL). Data sources: MEDLINE, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials were searched for the following terms: 'cerclage,' 'cervical cerclage,' 'salvage,' 'rescue,' 'emergency,' 'ultrasound-indicated,' 'short cervix,' 'cervical length,' 'ultrasound,' and 'randomized trial,' from inception of each database until November 2024. No language restrictions were applied. Study eligibility criteria: We included all randomized controlled trials (RCTs) of asymptomatic singleton pregnancies without prior spontaneous PTB screened with TVU CL, found to have a midtrimester short CL ≤25.9mm, and then randomized to management with either cerclage or no cerclage. We contacted corresponding authors of all the included trials to request access to the data and perform a meta-analysis of individual patient data. Study appraisal and synthesis methods: Individual patient data from the original RCTs were merged into a master database specifically constructed for the review. The primary outcome was PTB <37 weeks. The summary measures were reported as relative risk (RR) or as mean difference (MD) with 95% confidence interval (CI). To obtain the pooled risk ratio estimate the random effects model of DerSimonian and Laird were used RESULTS: Six trials, including 507 asymptomatic singleton gestations without prior spontaneous PTB and with short mid-trimester TVU CL ≤25.9mm, were included in the meta-analysis. The overall risk of bias of the included trials was judged as low. The primary outcome, PTB < 37 weeks, occurred in 89/266 (33.5%) vs 96/241 (39.8%) in the cerclage vs no cerclage group, respectively (RR 0.88, 95% CI 0.59-1.31). Planned subgroup analyses revealed that in patients with CL ≤20.9mm before 24 weeks, cerclage was associated with a significant decrease in PTB <37 weeks (56/181 (30.9%) vs 66/159 (41.5%); RR 0.75, 95% CI 0.56 to 0.99) and a significantly longer latency from randomization to delivery (p=0.049). Conclusions: In individuals with singleton gestations, without prior spontaneous PTB and with a short TVU CL in the second trimester, cerclage is associated with a significant decrease in PTB < 37 weeks and a significant longer latency at TVU CL ≤20.9mm before 24 weeks, but not an overall effect on TVU CL ≤25mm.