Description of a new technique for automatic sonographic measurement of variation of head-perineum distance and angle of progression during active phase of second stage of labor.

To evaluate the performance of a new ultrasound technique for the automatic assessment of the changes of the head-perineum distance (delta-HPD) and of the Angle of Progression (delta-AoP) during the active phase of the second stage of labour.Prospective observational cohort study including singleton term pregnancies with fetuses in cephalic presentation during the active phase of the second stage of labour. Using the transperineal approach, two short video clips of 10 sec each were recorded between the rest and the acme of two expulsive efforts to measure the AoP and the HDP. The clips were processed off-line and the changes of the two measurements (delta-HDP and delta-AoP) were calculated manually by experienced sonographers and using a new automatic system. The reliability of the algorithm was evaluated by comparing the automatic and the manual measurements, which were assumed as the reference gold standard.Overall, 27 women were included. A significant correlation between the results obtained through the automated and the manual reference methods was found for both parameters (Intra-CC = 0.97; Intra-CC =0.99). The values of the coefficient of determination (r = 0.98; r =0.98) and the low residual errors (root mean square error =1.2 mm; root mean square error = 1.5°) confirm the good accuracy provided by the algorithm. The Bland-Altman analysis showed a mean difference of 0.52 mm (limits of agreement, 2.10 mm) for the delta-HPD (p=0.034) and of 0.35° (limits of agreement, 2.83°) for the delta-AoP (p=0.39).The automatic assessment of delta-AoP and delta-HPD during pushing efforts is feasible. The automatic measurement of delta-AoP appears reliable when compared to gold standard measurement. This article is protected by copyright. All rights reserved.