Prediction of preterm delivery in twins by cervical assessment at 23 weeks

Objective To establish the relation between cervical length at 23 weeks of gestation in twin pregnancies and risk of spontaneous delivery before 33 we eks. Methods Cervical length was measured by transvaginal sonography at 23 (rang e 22-24) weeks of gestation in 464 twin pregnancies attending for routine a ntenatal care. In the patients who were managed expectantly the relation be tween cervical length and the rate of spontaneous delivery before 33 weeks was determined. Results The cervical length distribution was skewed to the left and the med ian value was 36 mm. The rate of spontaneous delivery before 33 weeks was i nversely related to cervical length at 23 weeks. It increased gradually fro m about 2.5% at 60 mm, to 5% at 40 mm and 12% at 25 mm, and exponentially b elow this length to 17% at 20 mm and 80% at 8 mm. Cervical length of 20 mm or less is found in about 8% of the population and this group contained abo ut 40% of women delivering spontaneously before 33 weeks. Conclusions In twin pregnancies measurement of cervical length provides use ful prediction of risk for spontaneous early preterm delivery.