TVS assessment of cervix better predictor of successful labor induction compared to Bishop's score: Study

It is a common practice in modern obstetrics in view of various obstetrical or medical indications. Usually, the decision to induce labor is made after considering the risk and benefits of prolonging the pregnancy. Successful induction results in vaginal delivery. However, the process is not completely seamless. Failure of induction can lead to cesarean section and the associated risks. It is therefore important to predict the chances of success of induction.

Efforts have been made to predict the rate of success of induction. Currently the most popular and widely used method is the Bishop’s score. It is a quantifiable but subjective method. Hence assessment is likely to vary from observer to observer. So the search for better predictors continues.

Trans-vaginal sonography (TVS) is an alternative but objective method emerging for assessing the cervix to predict the success of induction of labor by reducing interobserver variations. TVS measurements are quantitative and easy to reproduce, with minimal discomfort to the patient. It also allows a better evaluation of cervical length, since the supra-vaginal part of cervix is difficult to measure digitally. It also provides access to internal os, which cannot be reached in a closed cervix and where the effacement begins. Various parameters that can be used for cervical evaluation using TVS are cervical length, cervical funneling, cervical position, posterior cervical angle, distance of presenting part from external os, uterocervical angle, etc. Although many studies have been conducted to compare the Bishop’s score with TVS cervical evaluation, the superiority of one method over the other has not been clearly defined. In addition, there is a lack of definite and established cut offs to use TVS assessment in defining the success of induction. Some researchers have attempted to develop cut offs and scores to use the TVS assessment. However, these scores are not widely used at present. This might be because they used the parameters that are not easy to measure.

The aim of this study by Srivastava and Coumary A was to compare the two methods: Bishop’s score and MGM pre induction cervical scoring system (MGPICSS), and to develop an easy to use system for using TVS assessment to predict the successful induction of labor. This was an observational study conducted in a tertiary care center. 120 patients who met the selection criteria were included. Prior to the induction of labor the Bishop’s score and the sonographic scoring was assigned. Successful induction was defined as the patient entering the active phase of labor.

84% of participating women entered the active phase of labor. While 72.6% women had a normal vaginal delivery, 67.8% women delivered vaginally within 24 hours of induction. The TVS score (MGPICSS) of ≥2 predicted the successful induction with a specificity of 100% and sensitivity of 39.3% and AUC 0.74. In comparison, the Bishop score of ≥4 had a specificity of 75% and sensitivity of 44% and AUC 0.56. The prediction of delivery within 24 hours at the MGPICSS of ≥2 had a specificity of 100% and sensitivity of 42.9% and AUC 0.76. For the same, the Bishop’s score of ≥4 had specificity of 83.3% and sensitivity of 45.5% and AUC 0.71.

This study compared the Bishop’s score with the TVS assessment of cervix to predict the success of induction. It was concluded that the MGPICSS better predicted the successful induction of labor and also the delivery within 24 hours of the induction. TVS examination also causes less discomfort to the patients than digital examination.

TVS assessment of cervix is a better predictor of success of induction in comparison to Bishop’s score. According to the present study, MGPICSS of ≥2 can predict the successful outcome with specificity of 100% and sensitivity of 39.3%. Also a score of ≥2 can predict the chances of delivery within 24 hours with a specificity of 100% and sensitivity of 42.9%. MGPICSS is doable even by the beginners and has reduced interobserver variations.

Source: Srivastava and Coumary A / Indian Journal of Obstetrics and Gynecology Research 2024;11(2):276–280 https://doi.org/10.18231/j.ijogr.2024.053