Transperineal sonographic assessment of the angle of progression before the onset of labour: how well does it predict the mode of delivery in late-term pregnancy.

Abstract

Predicting the success of vaginal delivery is an important issue in preventing adverse maternal and neonatal outcomes. This study sought to examine whether measurement of the angle of progression (AoP) can predict asuccessful vaginal delivery following induction of labour (IoL) among late term nulliparous women with a low (4>) Bishop score. This prospective study included consecutive nulliparous pregnant women whose gestational age was 41weeks and 1-6days (late-term). The AoP was measured atleast three times and their means were calculated. During the study period, data of 150 women wereincluded in the final analysis. Thirty-eight women underwent CS due to failure to progress (n=30) or NRGHR (n=8), while the remaining 112 women underwent NVD, with four women requiring vacuum extraction. The two groups were similar with respect to age, gestational age, BMI, estimated foetal weight, and birth weight. Women undergoing NVD differed significantly from those undergoing CS with respect to a greater ultrasonographic AoP (113.8±11.9° vs. 98.1±10.9°, p=0.0001), a shorter duration of dinoprostone use, shorter time to labour contraction, and a shorter duration oflabour. In ROC analysis, the cut-off value for AoP was 100° for the prediction of successful IoL for NVD, with a sensitivity of 96 % and a specificity of 63 %. AoP may be a useful sonographic parameter for predicting successful vaginal delivery among nulliparous women at late term undergoing IoL; an AOP wider than 100°is associated with a high rate of vaginal delivery.