Dynamic changes of fetal head descent at term before the onset of labor correlate with labor outcome and can be improved by ultrasound visual feedback

Objective: The aim of the study was to evaluate the dynamic changes of angle of progression (AoP) before the onset of labor and their correlation with labor outcome and to investigate the effect of visual feedback using transperineal ultrasound on maternal pushing. Methods: We recruited a group of low-risk nulliparous women with singleton pregnancy at term. We measured AoP at rest, during pelvic floor contraction and Valsalva maneuver (before and after visual feedback). We compared AoP between women who delivered vaginally (VD) and those who underwent a cesarean section (CS). We also assessed the correlation between AoP and labor durations. Results: Overall, 222 women were included in the study; 129 (58.1%) had spontaneous VD, 35 (15.8%) had instrumental delivery, and 58 (26.1%) underwent CS. In comparison with rest, AoP decreased at PFMC (p <.001) and increased at first Valsalva (p <.001). AoP increased further significantly at Valsalva after visual feedback (p <.001). Women with VD had wider AoP at rest (p =.020), during Valsalva maneuver before (p =.024), and after visual feedback (p =.037). At cox regression analysis, wider AoP was associated with shorter first, second, and active second stages. Conclusion: Wider AoP at rest and under Valsalva is associated with vaginal delivery, the shorter interval to delivery, and shorter labor duration in nulliparous women at term. The accuracy of AoP in the prediction of cesarean delivery is modest and is unlikely to be clinically applicable in isolation for the prediction of the mode of delivery