Sonographic Elastography In Assessing Nulliparous Cervical Condition Before Labor Induction At Term

Backgroud and objective:To compare the ability of cervical sonoelastographic parameters and cervical length to predict the success of labor induction at term in nulliparous women.Methods:A total of 310 women with nulliparaous singleton term pregnancies scheduled for induction of labor were enrolled prospectively. Sonographic cervical length (CL) and elastographic stiffness assessment---elastography strain ratio (ESR) of total sagittal plane (TESR) and transverse internal os (IESR) were performed before cervical ripening treatment. Sonographers were blinded to outcomes of induction. Successful induction of labor was defined as active labor(cervical dilation >3cm, regular uterine contraction 3 times per 10 min)within 24h after cervical ripening treatment. who were not in active labor within 24 hours were assessed again at the time the ripening agent was removed. Receiver operation characteristics (ROC) curves of CL and ESR were drawn to assess predictive performance and best cut-off. Correlation analysis was also evaluated between CL and ESR. The intra-observer and inter-observer variability of measurements were assessed.Results:There were 218 pregnant women making successful induction and 92 failing in labor induction within 24 hours. The TESR and IESR in the group of successful and failure labor induction were 0.26±0.05,0.30±0.04 and 0.20±0.03,0.24±0.04, CL in the two groups were 28.39±6.52mm and 31.41±5.70mm (student's t test, P< 0.05). There were 51 women sonographic assessments taken pre and post cervical ripening, the TESR, IESR and CL were 0.21±0.03 vs 0.30±0.06 (P<0.05),0.24±0.05 vs 0.36±0.07 (P<0.05) and 30.82±5.68 vs 19.56±6.93mm (P<0.05). The sensitivity of TESR, IESR, and CL, in prediction of success of labor induction was 0.82,0.79,0.67; and the specificity and 0.74,0.68,0.56, the best cut-off value was 0.23,0.27,30mm, respectively. When CL and TESR or IESR were combined to make prediction of labor induction success, we did not find predictive value to be improved. There were no significantly correlation between TESR with CL or Bishop score (the coefficient was-0.088,0.024, P value was 0.122,0.67), as well as IESR with CL or Bishop score(the coefficient was -0.083,0.041, P value was 0.145,0.471).Conclusion:Sonoelastgraphy can objectively evaluate cervical ripeness before labor induction, the predictive value of ESR was better than CL. However, there was no role for either ESR or CL in predicting successul vaginal birth by labor induction.