Cervical Dilation and Risk of Delivery before 28 Weeks after Physical Exam–indicated Cerclage

Objective: To evaluate the association between the degree of cervical dilation at the time of physical exam–indicated cerclage and delivery before 28 weeks of gestation. Study Design: We conducted a retrospective cohort study of singleton pregnancies who underwent physical exam–indicated cerclage (painless cervical dilation ≥1 cm in the second trimester) at a single academic institution, 2014–2022. The primary outcome was delivery before 28 weeks. Cervical dilation was categorized as 1, 2, 3, and 4–5 cm. Multivariable logistic regression estimated adjusted odds ratios (aOR) with 95% confidence intervals (CI), adjusting for potential confounders. Kaplan-Meier analysis of the cerclage-to-delivery interval was examined as a sensitivity analysis. Results: Of 107 singleton pregnancies, 31 (29.0%) delivered before 28 weeks. Groups were similar except for BMI, which was higher among those who delivered before 28 weeks (34.6 ± 8.6 vs 30.8 ± 7.3 kg/m²; P=.026). Cervical dilation was greater in the early-delivery group (median 1.5 [IQR 1.0–3.0] vs 1.0 [IQR 1.0–2.0] cm; P=.016). Compared with 1 cm, dilation of 3 cm (aOR, 8.90; 95% CI, 1.75–45.30) and 4–5 cm (aOR, 12.95; 95% CI, 2.20–76.21) were independently associated with delivery before 28 weeks, whereas 2 cm was not (aOR, 0.74; 95% CI, 0.19–2.99); these estimates were imprecise because few patients had dilation of 3 cm or more. Median cerclage-to-delivery latency fell from 16.3 and 14.9 weeks at 1 and 2 cm to 2.4 and 1.5 weeks at 3 and 4–5 cm (log-rank P=.03). Conclusion: Greater cervical dilation at physical exam–indicated cerclage was associated with delivery before 28 weeks in a dose-dependent manner, with an apparent inflection between 2 and 3 cm. Because the higher-dilation strata contained few patients, these associations should be interpreted with caution.