Measuring angle of progression by transperineal ultrasonography to predict successful instrumental and cesarean deliveries during prolonged second stage of labor

Abstract

OBJECTIVE: To compare the angle of progression (AoP) measured by transperineal ultrasonography before indicating an instrumental delivery or cesarean delivery. METHODS: A prospective observational study was conducted among women with singleton term pregnancies with prolonged second stage of labor at Kwong Wah Hospital, Hong Kong, China, between May 16, 2011, and May 25, 2016. Transabdominal and transperineal ultrasonography were performed to determine fetal head position and AoP, respectively, both at rest and during uterine contraction with pushing. Mode of delivery was decided after vaginal examination without relying on ultrasonography. RESULTS: Of 143 women, 116 underwent successful instrumental delivery and 27 underwent cesarean delivery. Median AoP was 153.0° in the instrumental group versus 139.0° in the cesarean group at rest (P<0.001), and 182.5° in the instrumental group versus 156.5° in the cesarean group during contraction (P<0.001). The best predictive cutoff AoP for successful instrumental delivery was 138.7° at rest (sensitivity 86.2%, specificity 51.9%) and 160.9° during contraction (sensitivity 87.1%, specificity 74.1%). No between-group differences in AoP were found for ease of vacuum extraction at rest (P=0.457) or during contraction with pushing (P=0.095). CONCLUSION: The AoP predicted approximately 80% of successful instrumental deliveries performed for prolonged second stage of labor.