Cerclage for short cervix ≤20 mm 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 ≤25.9 mm, 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 ≤25.9 mm, 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 ≤20.9 mm 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 0.56–0.99) and a significantly longer latency from randomization to delivery (P=.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 ≤20.9 mm before 24 weeks, but not an overall effect on TVU CL ≤25 mm.