Prognostic accuracy of ultrasound measures of fetal head descent to predict outcome of operative vaginal birth: a comparative systematic review and meta-analysis

Objective: This study aimed to compare the prognostic accuracy of intrapartum transperineal ultrasound measures of fetal descent before operative vaginal birth in predicting complicated or failed procedures. Data Sources: We performed a predefined systematic search in Medline, Embase, CINAHL, and Scopus from inception to June 10, 2022. Study Eligibility Criteria: We included studies assessing the following intrapartum transperineal ultrasound measures before operative vaginal birth to predict procedure outcome: angle of progression, head direction, head-perineum distance, head-symphysis distance, midline angle, and/or progression distance. Methods: Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Bivariate meta-analysis was used to pool sensitivities and specificities into summary receiver operating characteristic curves for each intrapartum transperineal ultrasound measure. Subgroup analyses were performed for measures taken at rest vs with pushing and prediction of failed vs complicated operative vaginal birth. Results: Overall, 16 studies involving 2848 women undergoing attempted operative vaginal birth were included. The prognostic accuracy of intrapartum transperineal ultrasound measures taken at rest to predict failed or complicated operative vaginal birth was high for angle of progression (area under the receiver operating characteristic curve, 0.891; 9 studies) and progression distance (area under the receiver operating characteristic curve, 0.901; 3 studies), moderate for head direction (area under the receiver operating characteristic curve, 0.791; 6 studies) and head-perineum distance (area under the receiver operating characteristic curve, 0.747; 8 studies), and fair for midline angle (area under the receiver operating characteristic curve, 0.642; 4 studies). There was no study with sufficient data to assess head-symphysis distance. Subgroup analysis showed that measures taken with pushing tended to have a higher area under the receiver operating characteristic curve for angle of progression (0.927; 4 studies), progression distance (0.930; 2 studies), and midline angle (0.903; 3 studies), with a similar area under the receiver operating characteristic curve for head direction (0.802; 4 studies). The prediction of failed vs complicated operative vaginal birth tended to be less accurate for angle of progression (0.837 [4 studies] vs 0.907 [6 studies]) and head direction (0.745 [3 studies] vs 0.810 [5 studies]), predominantly because of lower specificity, and was more accurate for head-perineum distance (0.812 [6 studies] vs 0.687 [2 studies]). Conclusion: Angle of progression, progression distance, and midline angle measured with pushing demonstrated the highest prognostic accuracy in predicting complicated or failed operative vaginal birth. Overall, the measurements seem to perform better with pushing than at rest.