Background: To evaluate cervical length changes as predictors of preterm delivery. Methods: Two hundred and fifty-seven pregnant women underwent transvaginal ultrasound examination at 16 and 24 weeks of gestation. Cervical length was measured and the difference between the 2 measurements was calculated. The sensitivity, specificity, positive predictive value and negative predictive value of cervical length and cervical length changes were calculated and these methods were compared by receiver-operating characteristic (ROC) curve analysis. Results: Preterm delivery (before 37 weeks of gestation) occurred in 19 patients (7.4%). The mean cervical length was shorter in the preterm group, the area under the ROC curve for prediction of preterm delivery was 0.914, ultrasound had a sensitivity of 84.2% to predict preterm delivery with a false-positive rate of 18.5%, and the relative risk was 4.56 at the 34.3-mm cutoff value at 24 weeks of gestation. In contrast, a cervical length change on transvaginal ultrasound had a sensitivity of 73.3% to predict preterm delivery with a false-positive rate of 18.1%, and the relative risk was 4.08 at the 6.6-mm cutoff value. Conclusion: A single cervical length measurement obtained at 24 weeks of gestation can predict preterm delivery as accurately as cervical length change.

The objective of this study was to evaluate predictive value of cervical volume and length measurement for preterm delivery in low-risk pregnancies by transvaginal ultrasound. Two hundred fifty pregnant women were underwent ultrasound examination at 22 weeks of gestation by transvaginal route. Cervical length, width, and anteroposterior diameters were measured and cervical volume was calculated. All subjects were observed until term. Predictive values of cervical length and cervical volume were calculated and compared with predict preterm delivery. Preterm delivery occurred in 18 patients (7.2%). Mean cervical length and volume were statistically different between term and preterm delivered patients ( P = 0.001). Areas under curves were 0.913 for cervical volume and 0.923 for cervical length; this difference was not statistically significant ( P = 0.289). Sensitivity of cervical volume was 73.3% for 32-mL cut-off value with 12.85% false-positive rate and cervical length had 80% sensitivity at the 33.15-mm cut-off value with 12.7% false-positive rate. Cervical volume measurement by two-dimensional ultrasound did not add any benefit compared with the cervical length measurement for prediction of preterm delivery.

Cervical hCG expression seems to be rewarding in accurate diagnosis of preterm labor. This test has the advantage of low cost and wide availability.