Cervical length at 23 weeks in triplets: prediction of spontaneous preterm delivery.

OBJECTIVES: To establish the distribution of cervical length at 23 weeks of gestation in triplet pregnancies and to examine the relation to preterm delivery before 33 weeks. METHODS: Cervical length was measured by transvaginal sonography at 23 (range 22-24) weeks of gestation in 43 triplet pregnancies. The distribution of cervical length was determined and the relationship between cervical length and the rate of spontaneous preterm delivery before 33 weeks was calculated. RESULTS: The cervical length distribution was skewed to the left with a median of 34 mm. The rate of spontaneous labor and delivery before 33 weeks increased exponentially with decreasing cervical length at 23 weeks from 8% at 36-48 mm, to 11% at 26-35 mm, 33% at 16-25 mm and 67% at 15 mm or less. Cervical length was < or = 30 mm, < or = 25 mm and < or = 15 mm in 37%, 16% and 8% of cases, respectively, and the corresponding sensitivities in the prediction of spontaneous delivery before 33 weeks were 67%, 50% and 33%. CONCLUSIONS: In triplet pregnancies, measurement of cervical length provides a useful prediction of risk for spontaneous early preterm delivery.