Ultrasound Obstet Gynecol. 1998 Nov;12(5):312-7.

Cervical length at 23 weeks of gestation: prediction of spontaneous preterm delivery.
Heath VC, Southall TR, Souka AP, Elisseou A, Nicolaides KH.

Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, UK.

Objectives:

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.