Prediction of successful labor induction using transvaginal sonographic cervical measurements

Purpose:: To predict the success of labor induction by sonographic cervical measurements, maternal/obstetrical factors, and the Bishop's score. Methods:: Between February 2008 and February 2010, 190 consecutive pregnant women underwent clinical examination to assess the Bishop's score and transvaginal sonographic cervical measurements (cervical length, fetal head stage, and cervical dilatation) before labor induction. The following outcomes were analyzed: overall vaginal delivery and vaginal delivery up to 24 hours after labor induction. Results:: Overall vaginal delivery occurred in 133 (70.0%) patients and vaginal delivery 24 hours after labor induction happened in 119 (62.6%) patients. The sonographic cervical measurements were significantly associated with all outcomes (p < 0.01). The areas under the ROC curve (AUC) of all ultrasound cervical parameters to predict the two events were 68.9% and 72.0% (cervical length); 71.6% and 73.6% (fetal head stage); and 72.0% and 73.4% (cervical dilatation). Mathematical equations were obtained to calculate the probability for each event considering the sonographic cervical measurements in association with clinical factors after regression analysis, which increased the AUC for both events (80.1% and 79.3%). Conclusions:: Transvaginal sonographic cervical measurements can predict the successful labor induction, especially when associated to clinical analysis (Bishop's score).