Aim: To investigate the efficacy of uterocervical angle, posterior cervical angle, Bishop score and cervical length in predicting the success of labor induction in nulliparous patients during labor.

Methods: Our study was prospectively conducted on patients admitted to Etlik Hospital between November 2022 and June 2023 who opted for induction of labor. The mothers were between 18 and 40 years old, nulliparous and carrying a single live fetus with vertex between 37 and 41 weeks of gestation. 140 patients who met the criteria were examined by transvaginal sonography and digital cervical examination. The length of the cervix, the uterocervical angle and the posterior cervical angle, i.e. the angle between the uterus and the cervix, were measured by sonography and the Bishop score was determined by vaginal examination. The patients were divided into two groups, one successful and one unsuccessful vaginal delivery within 24 hours, and the outcome parameters were compared separately between the two groups. The target parameters were also compared by comparing patients separately by methods of cervical ripening with or without.

Results: Of the 140 pregnant women who participated in our study, 14 patients were excluded from the study due to a category III non-stress test (NST) and active vaginal bleeding. 61 patients delivered vaginally and 65 were delivered by cesarean section because vaginal delivery attempts were unsuccessful. There was no difference in demographic characteristics between the two groups, but weight and BMI were significantly higher in the group with unsuccessful deliveries. 
The length of the cervix was also significantly shorter in the group with successful induction (p=0.008). The cut-off value of the results of the ROC analysis curve for cervical length was 18.8 mm (AUC=0.632). While uterocervical angle (UCA) and Bishop scores were similar in both groups, vaginal delivery success was higher in patients in whom dilation and effacement were more advanced prior to induction (p=0.005). Although the posterior cervical angle (PCA) was quite high in the successful group, it was not statistically significant and predicted vaginal delivery only in the group of patients who received oxytocin and did not use cervical ripeners, it predicted vaginal delivery (p=0.022).

Conclusion: In conclusion, UCA and Bishop score measurements did not predict induction of labor at the time of delivery in the nulliparous pregnant women examined in this study. However, cervical length, posterior cervical angle, cervical dilation, and cervical effacement were found to be successful predictors of labor induction. We hypothesize that PCA and cervical length measurement are the most effective methods for predicting vaginal delivery in the group in which direct induction was induced due to various obstetric conditions and the induction was successful.

Nulliparous, Labor induction, Posterior cervical angle, Uterocervical angle, Cervical length