Cervical Length as a Predictor of Preterm Delivery in an Unselected Cohort of Women with Twin Pregnancies.

Objective: To determine the risk of spontaneous preterm delivery (SPTD) associated with transvaginal cervical length (TVCL) in an unselected cohort.

Study Design: This is a retrospective study of serial TVCLs in unselected twin gestations. Receiver operator curves for SPTD were constructed from TVCLs at 18, 20, 22, and 24 weeks. Prediction thresholds were determined using a false discovery rate of 10%. The risk of SPTD was compared with previously published, prospective data from a meta-analysis.

Results: A total of 1,228 women were included. SPTD occurred prior to 35 weeks in 232 (18.9%), 126 (10.3%), and 24 (2.0%) women prior to 35, 32, and 28 weeks. TVCL was most predictive at 22 weeks (area under the curve = 0.67). TVCL thresholds for predicting SPTD prior to 35, 32, and 28 weeks were 3.1, 3.0, and 2.9 cm. Compared with a previous meta-analysis, the risk of SPTD < 34, 32, and 28 weeks was lower (positive likelihood ratio 9.0 vs. 5.4, 10.1 vs. 5.9, and 9.6 vs. 4.3).

Conclusion: TVCL is modestly predictive of SPTD in twin gestations. Compared with previous prospective studies, this cohort has lower risk of SPTD at similar TVCLs.