Sonographic measurement of cervical length in twin pregnancies in threatened preterm labor.

OBJECTIVE To determine whether sonographic measurement of cervical length in twin pregnancies presenting with threatened preterm labor helps distinguish between true and false labor. METHODS In 87 women with twin pregnancies presenting with regular and painful uterine contractions at 24-36 (median, 30) weeks of gestation, cervical length was measured by transvaginal ultrasound. Women presenting in active labor, defined by the presence of cervical dilation of 3 cm or more, with ruptured membranes and those who underwent a prior or subsequent cervical cerclage, were excluded from the study. The clinical management was determined by the attending obstetrician without taking into account the cervical length. Primary outcome of the study was delivery within 7 days of presentation. RESULTS Delivery within 7 days of presentation occurred in 19/87 (22%) pregnancies and this was inversely related to cervical length, decreasing from 80% (4/5) at 1-5 mm, to 46% (6/13) at 6-10 mm, 29% (4/14) at 11-15 mm, 21% (4/19) at 16-20 mm, 7% (1/15) at 21-25 mm and 0% (0/21) at >25 mm. Logistic regression analysis demonstrated that significant independent contribution in the prediction of delivery within 7 days was provided by cervical length (odds ratio (OR) = 0.78, 95% CI 0.68-0.89, P < 0.001) and use of tocolytics (OR = 0.13, 95% CI 0.02-0.76, P = 0.024), with no significant contribution from gestation at presentation, chorionicity, ethnic origin, maternal age, body mass index, parity, previous history of preterm delivery, cigarette smoking, contraction frequency, vaginal bleeding or the administration of antibiotics or steroids. CONCLUSION In women with twin pregnancies presenting with threatened preterm labor, sonographic measurement of cervical length helps distinguish between those who deliver within 7 days and those who do not.