Predictive value of transvaginal ultrasonography for determining the response to tocolytic therapy in cases with preterm labour.

This study was performed prospectively on 144 randomly selected women carrying singleton uncomplicated pregnancies of 20 to 36 gestational weeks and 60 women with preterm labour matched for gestational age to determine the predictive value of transvaginal cervical measurements for evaluation of the response to tocolytic therapy. Cervical length and width and width of the cervical canal were measured and funnelling of internal os of the cervical canal was evaluated by transvaginal ultrasonography in each case. These measurements did not reveal any change depending on the gestational age in the control group. The mean values for cervical length and width, and width of cervical canal were 45.05+/-6.52 mm, 38.75+/-4.11 mm, 7.01+/-2.76 mm, respectively. Mean cervical length+/-standard deviations of the control group were used as cut-off values for the prediction of preterm delivery in the preterm labour group. When the cut-off value of the cervical length was accepted as 38.53 mm (-1 SD of the control group), the sensitivity, specificity, positive and negative predictive values for prediction of preterm delivery were 80.9%, 72.2%, 87.2%, 61.9%, respectively; whereas when this cut-off value was used in combination with the funnelling of the internal cervical os, the sensitivity and negative predictive value decreased to 40.5% and 41.9%, respectively; but the positive predictive value and specificity became 100.0% and 100.0%, respectively.