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Induction of labor is the most common intervention in modern obstetrics.
Success of the induction of labor is determined by the initial state of the cervix. Traditionally, preinduction cervical assessment is based on the digital examination of the cervix using the pelvic scoring system proposed by Bishop which is simple and easy to perform. Several studies have shown it to be subjective, with high inter- and intra-observer variation; it is found to be a poor predictor of the outcome of labor induction. Recently several authors have tried to find a more objective assessment of the cervix using transvaginal ultrasound for the prediction of outcome of labor induction.
The aim of this study is to assess the effectiveness of transvaginal measurement of cervical length & posterior cervical angle prior to induction of labor in prediction of successful induction and to compare its effectiveness with bishop score.
This study was conducted at the department obstetrics & gynecology, Ain Shams Maternity Hospital from the period of November 2018 to May 2019. A total of 70 women consented to participate in this study.
The 70 women 37-41weeks gestation underwent induction of labor due to passes due date, gestational diabetes, ROM, decrease fetal movement or preeclampsia .using 25μg misoprostol vaginally; the doses were given at 4 hours interval for maximum of 5 doses. Before induction the obstetrician performed a digital examination of the cervix and noted the Bishop score. Cervical length, posterior cervical angle were then measured by a transvaginal ultrasound. And when uterine contractions start external Cardiotocography was regularly performed to monitor the condition of the fetus.
In this study we found no statistically significant correlation between age, BMI, fetal birth weight and gestational age with success of induction of labor.
Successful induction of labor in this study correlated significantly with the Bishop score (p value 0.031), posterior cervical angle (p value <0.001), cervical length (p value 0.02) and rupture of membranes (p value 0.010).
The suggested cutoffs for the prediction of successful IOL were a PCA of more than 100°, a cervical length of less than 31 mm, and a Bishop score of more than 4.
Posterior cervical angle more than 100° had a higher sensitivity (87.8%) and specificity (86.2%) than cervical length and bishop score.
For cervical length sensitivity was (63.4%) and specificity was (58.6). and the Bishop score was (34.1%), (86.2%) respectively.
So, validity of posterior cervical angle, cervical length and Bishop Score as predictors of successful labor induction according to this study indicates that posterior cervical angle was more sensitive and specific predictor of successful labor induction than the Bishop score and cervical length.
Our results are compatible with those of the previous reports, that the ultrasound parameters are better indicators than the Bishop score for prediction of successful induction of labor. The limiting factors for the widespread use of the transvaginal sonography may be the cost of the equipment and a longer learning curve in comparison with Bishop Score. By integrating different parameters, like parity, cervical length and posterior cervical angle a risk scoring system may be created and validated in a larger population, which may be able to provide information to individual women about the outcome of labor induction.