Role of 'angle of progression' in prediction of delivery mode

The aim of this study was to investigate the role of the 'angle of progression' (AOP) in the prediction of vaginal delivery.

In this prospective study, we followed 70 singleton pregnant women. AOP was measured at admission time and also at the beginning of the second stage immediately after digital examination. Digital and ultrasound examiners were unaware of each other's results. The digital examiner decided on the delivery mode based on clinical assessment.

Sixty-five (92.9%) women had vaginal delivery. In the first stage of labor, the area under the curve was 87.5% (95% confidence interval [CI], 77.9-97.1; P = 0.005) for the AOP and 85.5% (95%CI, 75.2-95.6; P = 0.009) for digital examination and in the second stage of labor, the area under the curve was 90.2% (95%CI, 81-99.3; P = 0.003) for the AOP and 94.9% (95%CI, 89.1-100; P = 0.001) for digital examination. An AOP of ≥113° at the second stage was associated with a 90.8% probability of vaginal delivery.

We found a significant relation between AOP and cervical dilatation during the first stage of labor. A larger angle at the beginning of the second stage was significantly associated with shorter time to delivery.