Is cervical length evaluated by transvaginal ultrasonography helpful in detecting true preterm labor?

Objective: To investigate whether sonographic cervical markers can identify women in true preterm labor and predict delivery within 7 d and before 34 or 37 gestational weeks.Methods: This was a prospective observational study of women with singleton pregnancies and intact membranes given a diagnosis of preterm labor between 25 and 34 weeks and 6 d of gestation and who underwent transvaginal evaluation of the following characteristics: cervical length (CL), CL zeta score, absence of endocervical glandular echo, presence of cervical funneling, and presence of amniotic fluid sludge. The outcomes of interest were spontaneous delivery within 7 d of preterm labor and spontaneous delivery before 34 or 37 gestational weeks.Results: The inclusion criteria were met by 126 women, 31 (25%) of whom were excluded and 95 were analyzed. The median gestational age at admission was 31.9 weeks. The median CL at preterm labor was 22.3 mm (range: 0-42.8 mm). The delivery occurred within 7 d of presentation in 13 (13.7%) cases. Delivery before 34 weeks occurred in 16 (16.8%) cases and before 37 weeks in 40 (42.1%) cases. Logistic regression analysis showed CL in millimeters was an independent predictor of delivery within 7 d (OR 0.918, 95% CI 0.862-0.978, p = .008). For birth before 34 weeks, the predictor was gestational age at admission (OR 0.683, 95% CI 0.539-0.866, p = .002) and before 37 weeks, the presence of cervical funneling (OR 3.778, 95% CI 1.460-9.773, p = .006). The CL ≤ 15 mm had sensitivity and specificity values of 77 and 77%, respectively, and good accuracy (88%) for prediction of delivery within 7 d.Conclusion: The evaluation of the cervix by transvaginal ultrasound in women in preterm labor predicted delivery within 7 d and helped distinguish between true and false labor. The analysis of CL zeta score was not an independent factor to predict delivery in 7 d.