Cerclage for singleton pregnancies with an extremely short cervix (≤10 mm) and no history of spontaneous preterm birth: A multisite observational study

Introduction: There is uncertainty about the benefits of cerclage in patients with transvaginal cervical length (TVCL) ≤10 mm and no prior spontaneous preterm birth. Our aim was to assess whether cervical cerclage in these patients was associated with prolonged pregnancy latency. Methods: This was an observational study of asymptomatic singleton pregnancies without a history of spontaneous preterm birth with extremely short cervix (TVCL ≤10 mm) in the second trimester. Exposure and outcome data were extracted manually from medical charts by obstetric providers, with all outcomes occurring prior to study initiation. All patients were prescribed vaginal progesterone and those with a cervical dilation >1.5 cm were excluded. The primary outcome was time interval from diagnosis to delivery (or 37 weeks' gestation, whichever occurred first). Secondary outcomes included gestational age at delivery, mode of delivery, and neonatal outcomes. We adjusted for parity and used log-binomial regression to estimate the relative risk for categorical variables and linear regression to estimate mean differences for continuous variables. Results: There were 247 patients with TVCL ≤10 mm during anatomy scan. After exclusions, 87 remained, of which 55 (63.2%) received cervical cerclage. At the time of diagnosis, the mean cervical length was 5.8 mm (cerclage group) versus 7.4mm (no cerclage group, difference: -1.6, 95% CI -0.6, -2.6) and the gestational age was 21.0 weeks (cerclage group) versus 22.1 weeks (no cerclage group, -1.1, 95% CI -1.8, -0.3). Mean pregnancy latency was longer in the cerclage group compared to the no cerclage group (13.4 vs 11.1 weeks, 2.2, 95% CI -0.3, 4.9), though there was a high level of uncertainty in the estimate. Term delivery occurred 30% more often in the cerclage group compared to the no cerclage group (RR 1.31, 95% CI 0.96, 1.79). Conclusion: In our cohort, patients with extremely short cervix who received a cerclage had longer pregnancy latency than those who did not receive cerclage and more patients achieved term gestation, suggesting a potential benefit of cerclage in this population. However, given the high level of uncertainty of our estimates, additional research is needed to investigate these findings.