Sonographic measurement of cervical length and risk of preterm delivery

To study the relationship between cervical lengths measured by ultrasound and risk of preterm delivery.

We examined 209 women with singleton pregnancies. The inclusion criteria were women who presented with regular and painful contractions (≥2 contractions at intervals of 10 min for at least 1 h). Transvaginal scan was performed to measure the cervical length. The clinical management of the women, including hospitalization and administration of tocolytics, was determined by the attending obstetricians, who were blinded about cervical length. The primary outcome was delivery within 7 days of presentation.

Delivery within 7 days of presentation occurred in 19/209 (9%) of pregnancies who were presenting with regular and painful uterine contraction at 31 weeks of gestation, and this was inversely related to cervical length. Logistic regression analysis demonstrated that cervical length and history of abortion remain as significant contributors to predicting delivery within 7 days. Of the patients who presented with threatened preterm labor, 117 (56%) received tocolytics, and 92 (44%) did not. In the group with a cervical length of <15 mm, delivery within 7 days occurred in 15/21 (71.4%) who were treated with tocolytics and 2/5 (40%) that were managed expectantly.

Women with threatened preterm labor and a cervical length of <15 mm at presentation are at high risk of delivering preterm within 7 days. Sonographic measurement of cervical length helps to avoid over-diagnosis of preterm labor.