Associations of Cervical Features and Preventive Interventions With Gestational Age at Delivery

Objective The primary objective of this retrospective cohort study was to explore the associations between cervical anatomical features and gestational age at delivery in high-risk asymptomatic singleton pregnancies. A secondary exploratory objective was to evaluate gestational age at delivery according to preventive intervention strategy (Arabin pessary, cervical cerclage, or no intervention). Study design This retrospective cohort study included singleton pregnancies managed at a tertiary hospital between December 2019 and December 2024. Eligible pregnancies had documented cervical evaluation (length, diameter, and funneling), intervention status, and gestational age at delivery. The first available cervical measurement was analyzed. Very early preterm birth was defined as delivery before 33+0 weeks to focus on clinically significant prematurity associated with intensive neonatal care. Methods Categorical variables (cervical length: ≤2.4 cm vs. >2.4 cm, diameter: ≤10 mm vs. >10 mm, funneling yes/no, and intervention type) were compared using chi-square or Fisher's exact tests. Gestational age distributions among intervention groups were assessed using kernel density plots and boxplots. Time-to-delivery was evaluated using Kaplan-Meier curves and log-rank testing. Multivariable Cox proportional hazards models included intervention type (reference: cerclage), cervical length, diameter, and funneling. Given the limited number of events, multivariable estimates were interpreted cautiously because of potential overfitting and type II error. Results Among 174 singleton pregnancies, 30 (17.2%) delivered before 33 weeks, whereas 144 (82.8%) delivered at ≥33 weeks. Cervical diameter >10 mm was less frequent among pregnancies delivering before 33 weeks (3/30, 10%) compared with those delivering at ≥33 weeks (63/144, 43.8%; p<0.001). Funneling was more frequent in the <33-week group (15/30, 50.0%) than in the ≥33-week group (51/144, 35.4%), although this association did not reach conventional statistical significance in multivariable modeling (p=0.107). Kaplan-Meier analyses suggested longer gestation in the pessary and cerclage groups compared with no intervention, but between-group differences were not statistically significant (log-rank p=0.08). In adjusted Cox models, diameter ≤10 mm was associated with a lower hazard of delivery (HR: 0.398, 95% CI: 0.205-0.433; p<0.001). Other covariates were not statistically significant. Conclusion Cervical diameter was associated with gestational age at delivery in this cohort and may represent a candidate marker for risk stratification in high-risk singleton pregnancies. Because of the retrospective design, limited event numbers, and potential indication bias in intervention assignment, these findings should be interpreted as hypothesis-generating rather than definitive evidence of intervention effectiveness or equivalence. Larger prospective and multicenter studies are needed.