Longitudinal Ultrasound Evaluation of Cervical Length for Predicting Spontaneous Preterm Delivery Before 34 Weeks in Twin Gestations: A Retrospective Cohort Study

Background/Objectives: This study evaluated whether sequential changes in cervical length (CL) can predict spontaneous preterm birth (sPTB) before 34 weeks of gestation in twin pregnancies. Methods: This retrospective study from a single tertiary-care center analyzed 349 twin pregnancies with deliveries between January 2019 and December 2023. Cervical length assessments began at 18–21 weeks, followed by biweekly serial measurements. The primary outcome was sPTB before 34 weeks. CL changes were assessed descriptively using data from patients with and without sPTB before 34 weeks. We defined the high-risk status for sPTB based on our assessment. Logistic regression models were used to compute the odds ratios (ORs) and 95% confidence intervals (CIs) to quantify the relationship between these predictors and sPTB. Diagnostic accuracy was assessed from the area under the curve using receiver operating characteristic curve analysis. Results: The sPTB rate before 34 weeks of gestation was 8.5% (18/212). In the group without -sPTB before 34 weeks of gestation, the 5th percentile CL was approximately 20 mm at 25 weeks and 15 mm at 26–27 weeks of gestation. Sequential CL measurements revealed that a rapid shortening of ≥10 mm within 2 weeks significantly predicted sPTB before 34 weeks. A decrease in CL of ≥10 mm in a 2-week interval was associated with increased odds for sPTB before 34 weeks of gestation [adjusted OR (95% CI): 6.66 (2.32–19.14)]. Conclusions: In twin pregnancies, measuring CL every 2 weeks after approximately 20 weeks of gestation may facilitate sPTB detection before 34 weeks.