Longitudinal cervical‐length trajectories and extreme preterm birth in twin pregnancy

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. Figure S1 Forest plot showing adjusted hazard ratios (HRs) () with 95% CIs (horizontal lines) for each cervical-length (CL) trajectory group (Group A, mean CL remained ≥ 30 mm throughout pregnancy (n = 171); Group B, mean CL decreased to < 30 mm at approximately 26–30 weeks (n = 152); and Group C, mean CL shortened to < 20 mm by around 23 weeks (n = 25)) according to gestational-age-based sPTB classification (extreme, 22 + 0 to 27 + 6 weeks; very-to-moderate, 28 + 0 to 33 + 6 weeks; and late, 34 + 0 to 36 + 6 weeks), based on cause-specific Cox proportional hazards models adjusted for maternal age, body mass index, parity and history of sPTB, and using Group B as the reference group (vertical dashed line, subdistribution hazard ratio = 1). NA (not available) indicates that the model could not be estimated owing to absence of events. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.