Two-stage transvaginal cervical length screening for preterm birth in twin pregnancies

To compare cervical length (CL) at 18-21 and 22-25 weeks' gestation in twin pregnancies in prediction of spontaneous preterm delivery and to examine cervical shortening.

Retrospective cohort study of CL measured at 18-21 and 22-25 weeks' gestation in twin pregnancies.

Receiver operating characteristics (ROC) curve revealed area of 0.64 (95% CI 0.53-0.75) and 0.80 (95% CI 0.72-0.88) for measurements at 18-21 and 22-25 weeks, respectively (Por=2 mm/week. Sensitivities of 80% and 60.8% and NPV of 98.9% and 90.6% for delivery at <28 and <34 weeks gestation were reached.

In twin gestations, assessment of CL at 22-25 weeks is better than assessment at 18-21 weeks to predict preterm delivery before 34 weeks. Cervical shortening at a rate of >or=2 mm/weeks between 18 and 25 weeks gestation was a good predictor of spontaneous preterm birth in this high-risk population.