Utility of Ultrasonographic Parameters for Monitoring of Progress of Labor and Prediction of Successful Vaginal Delivery: Narrative Review

Abstract

Traditionally, progress of labor and the prediction of vaginal delivery is done by clinical assessment. There is a lot of subjectivity in assessment and increased interobserver variability, especially with digital vaginal examination. For the past two decades, many ultrasonographic parameters were developed, and their utility was studied objectively. Of the ultrasound (USG) parameters, head position is the easiest to recognize. The descent and station of the head are determined indirectly by angle of progression (AOP) and head perineal distance (HPD). Cervical dilatation does not correlate well with digital vaginal examination, and it is difficult to visualize cervical rim beyond 8-cm dilatation. Midline angle and head-up position are other parameters in the second stage of labor that are determined to predict difficult vaginal delivery. Angle of progression of >110° and HPD <4 cm are good predictors of vaginal delivery. "Sonopartogram" may replace the traditional partogram as it is more objective, noninvasive, and women-friendly. Intrapartum apps are incorporating USG parameters with other patient characteristics to develop models for predicting vaginal delivery.