Prediction of mode of delivery by an ultrasound score similar to Bishop score and performance of independent predictors.

Abstract

There is evolving literature on the superiority of transperineal ultrasound (TPU) in predicting the mode of delivery either before induction or during the course of labour. An ultrasound score (USG score) similar to a Bishop score or an ultrasound scoring method based on independent predictors before the onset of labour at term gestation would serve as a baseline objective record over which further progress of labour could be evaluated. 1. To sonographically examine the clinical parameters evaluated during a digital examination. 2. To derive an USG score using TPU parameters, similar to a Bishop score, and determine its performance in predicting pregnancy outcomes. 3. To identify which are the independent predictors of caesarean section among all the studied ultrasound (USG) parameters. In this prospective study, all the eligible women who came for routine antenatal care at term gestation and who were due for pelvic assessment were recruited. They underwent transabdominal ultrasound (TAS) for evaluating head position and head circumference, and TPU for evaluating head station with and without applying fundal pressure, various cervical parameters, sub pubic angle. Equivalent five USG parameters were scored along similar lines as the Bishop score. These women underwent vaginal examination for Bishop score and pelvic adequacy by an obstetrician who was blinded about USG parameters. While spontaneous onset of labour (SOL) was awaited in some of these women, some were induced as and when indicated. After delivery, the Bishop scores, pregnancy outcome in terms of SOL or induction of labour (IOL), mode of delivery and duration of labour were noted retrospectively from case records. Independent predictors of caesarean were obtained by univariate and multivariate analysis. All the parameters were assessed for predictive ability of caesarean section by univariate analysis. The cervical length, angle of progression (AOP) at rest, head perineal distance (HPD) at rest and with pressure, Bishop score and USG score were found significant. On multivariate analysis, cervix length and USG score were found to be statistically significant. At a USG score of ≤ 5, the sensitivity and specificity to predict caesarean section were 84% and 68%, respectively. The relative risk (RR) was 4.9 (95% CI 2.3-12). The USG score could predict SOL. The p value was 0.001. The area under the curve (AUC) for the ultrasound score was 0.74. USG examination by USG score at term gestation before the onset of labour can predict mode of delivery by caesarean section. It can predict spontaneous onset of labour. However, among all the individual parameters, cervix length has best predictive ability for caesarean section.