(896) Prognostic accuracy of ultrasound measures of fetal descent to predict outcome of operative vaginal birth

To compare the prognostic accuracy of transperineal ultrasound (TPUS) measures of fetal descent prior to operative vaginal birth (OVB) in predicting complicated or failed procedure.

Study Design: We performed a predefined systematic search in Medline, Embase, CINAHL and Scopus. We included studies assessing the following TPUS measures prior to OVB to predict procedure outcome: Angle of progression (AOP), head direction (HD), head perineum distance (HPD), midline angle (MLA) and/or progression distance (PD). 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 TPUS measure. Sub-group analysis was performed for measures at rest versus with pushing and prediction of failed versus complicated OVB.

Results: 15 studies involving 2,440 women undergoing attempted OVB were included. The overall prognostic accuracy was high for AOP (AUC 0.89 [n=8 studies]) and PD (0.90 [n=3]), moderate for HD (0.79 [n=6]) and HPD (0.76 [n=7]) and fair for MLA (0.64 [n=4]). Subgroup analysis of measures taken with pushing demonstrated higher AUC for AOP (0.93 [n=4]) and PD (0.93 [n=2]), predominantly due to increased specificity, considerably higher AUC for MLA (0.90 [n=3]) and similar AUC for HD (0.82 [n=4]). Prediction of failed compared to complicated OVB was less accurate for AOP (0.77 [n=3] vs 0.91 [n=6]) and HD (0.75 [n=3] vs 0.81 [n=5]), predominantly due to a drop in specificity, and more accurate for HPD (0.81 [n=5] vs 0.65 [n=2]).

Conclusion: AOP, PD, and MLA measured with pushing demonstrate the highest prognostic accuracy in predicting complicated or failed OVB. Overall, AUC tends to be higher for TPUS performed with pushing compared to at rest. Accuracy of predicting failed compared to complicated OVB is higher for HPD, whereas the specificity of AOP and HD is reduced. Further studies are required to define how TPUS could best guide clinical practice and if this can improve maternal or neonatal outcomes of OVB.