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

Objectives To compare the prognostic accuracy of intrapartum transperineal ultrasound (ITU) measures of fetal descent prior to operative vaginal birth (OVB) in predicting complicated or failed procedure. 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 ITU measures prior to OVB to predict procedure outcome: Angle of progression, head direction, head-perineum distance, head-symphysis distance, midline angle and/or progression distance. Study appraisal and synthesis methods Study quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Bivariate meta-analysis was used to pool sensitivities and specificities into summary receiver-operating characteristic curves for each ITU measure. Subgroup analyses were performed for measures taken at rest versus with pushing and prediction of failed versus complicated OVB. Results Sixteen studies involving 2,848 women undergoing attempted OVB were included. The prognostic accuracy of ITU measures taken at rest to predict failed or complicated OVB was high for angle of progression (area under the curve [AUC] 0.891, 9 studies) and progression distance (AUC 0.901, 3 studies), moderate for head direction (AUC 0.791, 6 studies) and head-perineum distance (AUC 0.747, 8 studies) and fair for midline angle (AUC 0.642, 4 studies). There were no studies with sufficient data to assess head-symphysis distance. Subgroup analysis showed that measures taken with pushing tended to have a higher AUC for angle of progression (0.927, 4 studies), progression distance (0.930, 2 studies) and midline angle (0.903, 3 studies), with similar AUC for head direction (0.802, 4 studies). Prediction of failed compared to complicated OVB 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 due to lower specificity, and was more accurate for head-perineum distance (0.812, 6 studies vs 0.687, 2 studies). Conclusions Angle of progression, progression distance and midline angle measured with pushing demonstrate the highest prognostic accuracy in predicting complicated or failed OVB. Overall, measurements seem to perform better with pushing compared to at rest.