Non-invasive transperineal ultrasound is used to detect the descent of the fetal head by measuring head-perineum distance (HPD) and angle of progression (AP). The aim of the study was to evaluate HPD and AP as predictors of vaginal delivery in the first stage of labor. Methods: A prospective cohort study was made in Riga Maternity Hospital in Latvia in 2016. In the study were included nulliparous women with singleton pregnancies in cephalic presentation. HPD and AP were measured using

more »

... eal ultrasoud. Demographic data, delivery parameters and birth outcomes were collected. Results: Of 36 women enrolled in the study, 26 (72.2%) had a vaginal delivery. The area under the receiver–operating characteristics curve was 0.865 (95% confidence interval (CI) 0.75-0.98) for the prediction of vaginal delivery using HPD as the test variable. The area under the curve was 0.877 (95% CI 0.77-0.99) using AP. All women delivered vaginally, if HPD was ≤40 mm (18 (50%) women). 8 (22.2%) of 18 women with HPD >40 mm delivered vaginally (P<0.001). 21 women of 22 (61.1%) with AP ≥105° delivered vaginally. In the other 14 (38.9%) women with AP <105° 5 delivered vaginally (P<0.001). Conclusions: Both HPD ≤ 40 mm and AP ≥ 105° are predictors for vaginal birth in the first stage of labor.