Ultrasound assessment of cervical length in threatened preterm labor.

OBJECTIVE More than 70% of women presenting with threatened preterm labor do not progress to active labor and delivery. The aim of this study was to investigate the hypothesis that in women with threatened preterm labor, sonographic measurement of cervical length helps distinguish between true and false labor. METHODS We examined 216 women with singleton pregnancies presenting with regular and painful uterine contractions at 24-36 (mean, 32) weeks of gestation. Women in active labor, defined by the presence of cervical dilatation > or = 3 cm, and those with ruptured membranes were excluded. On admission to the hospital a transvaginal scan was performed to measure the cervical length. The subsequent management was determined by the attending obstetrician. The primary outcome was delivery within 7 days of presentation. RESULTS In 173 cases the cervical length was > or = 15 mm and only one of these women delivered within 7 days. In the 43 cases with cervical length < 15 mm delivery within 7 days of presentation occurred in 16 (37%) including 6/14 (42%) treated with tocolytics and 10/29 (35%) managed expectantly. Logistic regression analysis demonstrated that the only significant contributor in the prediction of delivery within 7 days was cervical length < 15 mm (odds ratio = 101, 95% CI 12-800, P < 0.0001) with no significant contribution from ethnic group, maternal age, gestational age, body mass index, parity, previous history of preterm delivery, cigarette smoking, contraction frequency or use of tocolytics. CONCLUSIONS In women with threatened preterm labor, sonographic measurement of cervical length helps distinguish between true and false labor.