Cervical length at 23 weeks in twins in predicting spontaneous preterm delivery

To establish the relationship between cervical length at 23 weeks' gestation in twin pregnancies and risk of spontaneous preterm delivery.

Cervical length was measured during routine antenatal care by transvaginal sonography at 23 (range 22-24) weeks' gestation in 215 twin pregnancies. Distribution of cervical length was determined, and sensitivity and false-positive rate for spontaneous preterm delivery at or before 28, 30, 32, and 34 weeks for cutoff cervical lengths of 15, 25, 35, and 45 mm were calculated.

Cervical length distribution was skewed toward shorter length and the median value was 38 mm. In 11.2% and 4.2% of cases, length was up to 25 mm and up to 15 mm, respectively. The spontaneous delivery rates at or before 28, 30, 32, and 34 weeks were 3.8%, 4.7%, 8.0%, and 17.5%, respectively, and were not statistically significantly related to any demographic characteristics, obstetric history, or chorionicity. Sensitivity to predict spontaneous preterm delivery was 100%, 80%, 47%, and 35% for 28, 30, 32, and 34 weeks, respectively, for cervical length up to 25 mm. The corresponding sensitivity values for cervical lengths up to 15 mm were 50%, 40%, 24%, and 11%. The rate of spontaneous delivery at or before 32 weeks increased exponentially with decreasing cervical length at 23 weeks, from 2.9% at or greater than 46 mm, to 4.3% at 36-45 mm, 6.7% at 26-35 mm, 31% at 16-25 mm, and 66% at 15 mm or less.

Measurement of cervical length in twin pregnancies predicted risk of spontaneous early preterm delivery.