Validation of Cesarean risk assessment nomogram and assessing the effect of Cervical Ripening Balloon and Evening Primrose Oil compared to Misoprostol on bishop score and duration of first stage of labor

Abstract

Background: In order to reduce the complications of postdate pregnancy, induction of labor is done using chemical drugs and complementary therapies. Given that about one-third of 22% of cases of labor induction eventually lead to cesarean section, it may be crucial to estimate the likelihood of cesarean section before deciding to induce labor, Due to the lack and unuse of the online Labor induction calculator tool in IRAN, localization of this tool seems necessary. On the other hand, Evening Primrose Oil (EPO) is one of the new herbal medicines that have recently received worldwide attention for use in cervical ripening, but there is not enough clinical evidence in its use; CRB (Cervical Ripening Balloon) is also a new non-pharmacological method which according to the conducted studies is an effective method without side effects, so this study aimed to compare the effect of CRB and vaginal EPO with vaginal misoprostol on Bishop's score and the duration of the first stage of labor.Methods: This study was performed in two phases, the first phase was a prospective descriptive-analytical study and the second phase was a randomized controlled clinical trial that was conducted in Taleghani, Al-Zahra and 29 Bahman hospitals of Tabriz. The first phase was conducted on 300 cases (200 for developing and 100 for validating of nomogram) from September 2020 to June 2021. Eligible women were selected by convenience sampling and a checklist was completed that included height, current body mass index, parity, gestational age and modified bishop score. Participants were followed up until delivery and the type of delivery was recorded in the relevant checklist. The labor induction prediction nomogram was developed and validated. Multivariate logistic regression was used to determine the predictors of cesarean delivery after induction. Differentiating power of each model was evaluated using Area Under Curve (AUC). In the second phase, in a double-blind randomized clinical trial from December 2020 to December 2021, 90 women were randomized to 3 groups and received the following interventions. 25 micrograms of vaginal misoprostol or 4000 mg of vaginal EPO every 4 hours for at least 2 doses or CRB. The data were analyzed with one-way analysis of variance (ANOVA One-Way) and Chi Square Test.Results: The results of phase one showed that cesarean section was conducted in 80 cases (26.7%) out of 300 labor inductions, 56 cases were nulliparous and 24 cases were multiparous . Among all the variables, based on multivariate logistic regression, cesarean risk assessment was the only variable predicting the type of delivery [OR = 1.07 (CI 95% 1.01-1.12) P = 0.012]. AUC was calculated 0.67 for the nomogram development group and 0.71 for the validation group. This model was used to predict the probability of cesarean section after labor induction in the development group with specificity of 98.18 and negative predictive value of 75.52 and in the validation group with specificity of 93.65 and negative predictive value of 74.68. It has relatively good validity in predicting the risk of cesarean section.The results of the second phase showed that there was not statistically significant difference between misoprostol group and EPO group in the average bishop score 4 hours after the intervention (P=0.186), but it was significantly higher in the EPO group 8 hours after the intervention (mean difference: 0.94; 95% CI: 1.83 to 0.05) ). Due to the expectant management of the CRB and the impossibility of vaginal examination before catheter removal, it was not possible to compare the Bishop score 4 and 8 hours later with the other two groups, but the Bishop score of this group increased significantly when compared with before insertion (P=0.001). In terms of other outcomes, including the length of the first stage of labor (P=0.192), the second stage of labor (P=0.298), the third stage of labor (P=0.764), the rate of cesarean section (P=0.709), the first minute Apgar score (P=0.384), the use of oxytocin (P=0.252) and the occurrence of adverse events (P=0.638) there were not significant differences between groups.The average score of birth satisfaction score in the EPO group was significantly higher than the other groups (P=0.018).Conclusion: The caesarean risk assessment model had a relatively good validity in predicting cesarean section risk, it can be used to strengthen counseling of women undergoing labor induction with low Bishop scores and finally to improve maternal health and birth outcomes. Also, considering that EPO and CRB were as effective as misoprostol in improving Bishop score before induction, and even this effect was greater in the second dose of EPO than misoprostol. Therefore, oral and vaginal EPO consumption can be recommended from week 38 onwards, especially in mothers with a history of post-term pregnancy, as a cervical ripening. On the other hand CRB can be inserted 12 hours before hospitalized on an outpatient basis to speed up the preparation of the cervix and reduce the duration of the mother's hospitalization.