Cervical dilation staging and early preterm birth risk after exam-indicated cerclage: A Retrospective Cohort Study with the International Collaborative for Cerclage Longitudinal Evaluation and Research (IC-CLEAR).

Background: Preterm birth is a leading cause of neonatal morbidity and mortality. The risk of preterm birth, especially early preterm birth, and pregnancy loss is significantly increased in patients with premature cervical dilation. An intervention to reduce risk of preterm birth in this setting is cerclage, however, counseling on risk of preterm birth and neonatal outcomes based on different cervical examination findings at time of cerclage placement is difficult given limited data evaluating these differences.

Objective: We aimed to determine how the cervical exam staging criteria by Roman et al. (2023) prior to placement of exam-indicated cerclage was associated with risk of very early preterm birth<28 weeks.

Methods: This is a retrospective analysis utilizing the International Collaborative-Cerclage Longitudinal Evaluation and Research (IC-CLEAR) database, a multi-center international retrospective database of singleton pregnancies that received a cerclage. Our study included participants who received a physical examination-indicated cerclage. The predictor of interest was cervical stage assessed pre-operatively, evaluated as an ordinal variable with progressive severity indicated by advancing stage- Stage 3 (visually closed, manually dilated with palpable membranes), Stage 4A (visually dilated, membranes seen but not to external os), Stage 4B (visually dilated, membranes at external os), Stage 4C (visually dilated, membranes past external os). The primary outcome was preterm birth <28 weeks gestation. Secondary outcomes included preterm birth <34 weeks, preterm birth <37 weeks, and latency from cerclage placement to delivery. Multivariate analysis was conducted adjusting for study site, prior preterm birth, gestational age at cerclage placement, use of perioperative antibiotics or indomethacin, and progesterone use after cerclage placement.

Results: The analysis included 81 patients who had placement of a physical examination-indicated cerclage and met the inclusion criteria. The number of patients in Stages 3, 4A, 4B, and 4C were 17, 27, 25, and 12, respectively. Multivariate analysis revealed advanced cervical stage is significantly associated with preterm birth <28 weeks (overall p-value 0.003). Rates of preterm birth <28 weeks by stage were: 3 (11.7%), 4A (25.9%), 4B (44.0%), 4C (75.0%). Adjusted odds ratio for preterm birth by progressive cervical stage compared to Stage 3 were: Stage 4A (aOR 2.4, 95% CI 2.4 (0.31-19.25), P=0.40), Stage 4B (aOR 8.7, 95% CI (1.2-63.9), P=0.03), Stage 4C (aOR 43.73, 95% CI (3.3-572.2), P=0.004). Latency to delivery after cerclage decreased with increasing Roman stage, although this was only statistically significant for Stage 4C.

Conclusion: Cervical staging based on dilation and degree of membrane prolapse helps risk stratify patients presenting with advanced cervical dilation with successful cerclage placement and may be a useful tool for counseling and management.