Transperineal sonographic assessment of the angle of progression as a predictor of a successful vaginal delivery following induction of labor.

Research paper by Moshe M Gillor, Edi E Vaisbuch, Svetlana S Zaks, Oren O Barak, Zion Z Hagay, Roni R Levy

Indexed on: 12 Apr '16Published on: 12 Apr '16Published in: Ultrasound in Obstetrics & Gynecology


The aim of this study was to assess whether the angle of progression (AOP) measurement before induction of labor (IOL) can predict a successful vaginal delivery in primiparous women.We conducted a prospective, observational study including nulliparous women with singleton pregnancies, at term, with an indication for IOL. Transperineal sonography was used to measure the AOP before cervical ripening in consenting women. Since all women enrolled had a low Bishop score, 98.6% of them were induced with either intra-cervical extra-amniotic balloon catheter or vaginal prostaglandin E2. The staff in the labor ward was blinded to the AOP measurements. Clinical data was retrieved from computerized medical records.Of the 150 women included in the final analysis, 40 (26.6%) were delivered by cesarean section. The median AOP was narrower in women who eventually had a cesarean delivery than in those who delivered vaginally (90(0) , IQR 84-94.5(0) vs. 98(0) , IQR 90.75-105(0) , respectively; p < 0.001). When including only women who underwent cesarean delivery due to a non-progressive labor (n = 27), an AOP >92(0) (derived from an ROC curve) was associated with a successful vaginal delivery in 94.8% of women. A multivariate stepwise logistic regression analysis including maternal age, body mass index, gestational age, estimated fetal weight, fetal head station, indication for IOL and the AOP demonstrated that only the later was independently associated with the prediction of a successful induction.This study suggests that the AOP may be a useful sonographic parameter to predict a successful vaginal delivery among nulliparous women at term undergoing labor induction. An AOP wider than 92(0) was associated with a high rate of vaginal delivery.

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