Quantitative sonoelastography of the uterine cervix prior to induction of labor as a predictor of cervical dilation time

Objective. To evaluate how the approximate Young's modulus of the uterine cervix assessed by quantitative sonoelastography in patients undergoing induction of labor is associated with the cervical dilation time and to evaluate the approximate Young's modulus as a predictor of prolonged cervical dilation time. Design. Cross-sectional study. Setting. Aarhus University Hospital, Aarhus, Denmark. Population. Term-pregnant women. Methods. A total of 49 term-pregnant women were included before induction of labor. The approximate Young's modulus of the anterior cervical lip was determined by the use of a reference cap applied on the end of the transvaginal transducer during sonoelastography. Main outcome measures. Cervical dilation time during active labor. Results. The approximate Young's modulus was associated with the cervical dilation time during active labor (R-log(2) = 0.24, p < 0.01) and predicted prolonged duration of cervical dilation time (>330 min) with the area under the receiver operating characteristic (ROC) curve of 0.71, sensitivity 74%, and specificity 69%. Equivalent figures for the Bishop's score were R-log(2) = 0.02 (p = 0.37), the area under the ROC curve 0.53, sensitivity 53%, and specificity 46%. For the cervical length measurements the corresponding results were: R-log(2) = 0.02, p = 0.35, area under the ROC curve 0.57, sensitivity 66% and specificity 54%. The intra-observer and inter-observer intraclass correlations were 88% and 58%, respectively, with quantitative elastography. Conclusions. The approximate Young's modulus is superior to the Bishop score and the cervical length measurements concerning the prediction of cervical dilation time and the risk of prolonged dilation time after induction of labor.