Clinical Efficacy of Cervical Length and Volume for Prediction of Labor Onset in VBAC Candidates

BACKGROUND The purpose of this research is to discover whether measurement of cervical length and cervical volume at term is helpful in predicting the onset of labor in VBAC candidates. METHODS Transvaginal sonographic evaluations of the cervixes of pregnant women who desired to undergo VBAC were performed between 36 - 40 weeks gestation. Clinical information such as labor onset time, gestational age at delivery and delivery mode was gathered from medical records. RESULTS A total of 514 pregnant women participated in this study. Cervical length was significantly longer in the group that delivered 7 days or more after measurement than in the group that delivered within 7 days of measurement (43±0.77 cm vs. 2.99±0.72 cm, p< 0.001). Cervical volume was significantly larger in the group that delivered at and after 7 days than in the group that delivered within 7 days (29.21±11.62 cm(3) vs. 34.07±13.41 cm(3), p=0.014). The cervical length ROC curve was significantly more predictive than the cervical volume ROC curve (AUC: 0.711 vs 0.594, p= 0.001). There were no significant differences between the combined cervical length/volume ROC curve and the cervical length ROC curve alone (p= 0.565). The AUC of the cervical length ROC curve to predict postterm pregnancy was 0.729. CONCLUSION Measuring cervical length is helpful in predicting the onset of spontaneous labor within 7 days and posterm delivery in VBAC candidates.