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

OBJECTIVE To examine the potential value of routine measurement of cervical length in singleton pregnancies at 23 weeks of gestation in the prediction of the risk for early spontaneous preterm delivery. METHODS Cervical length was measured by sonography at 23 weeks in 2567 singleton pregnancies in women attending for routine antenatal care. In 43 women, the length was < or = 15 mm and 21 of these were managed expectantly, whereas in 22 cases a cervical cerclage was placed. In the pregnancies that were managed expectantly, the relation between cervical length and preterm delivery was examined and the risk of spontaneous delivery at < or = 32 weeks was estimated. RESULTS Cervical length at 23 weeks was < or = 15 mm in 1.7% of cases; this group contained 86%, 58% and 20% of pregnancies that delivered spontaneously at < or = 28, < or = 32 and < or = 36 weeks, respectively. The risk for delivery at < or = 32 weeks decreased from 78% at a cervical length of 5 mm to 4% at 15 mm and 0.5% at 50 mm. CONCLUSIONS Cervical length at 23 weeks is < or = 15 mm in < 2% of the population; this group contains about 90% and 60% of the women delivering at < or = 28 and < or = 32 weeks, respectively. Measurement of cervical length provides accurate prediction of risk for early preterm delivery.