Uncertain fetal head engagement: a prospective randomized controlled trial comparing digital exam with angle of progression

Abstract

Background: Uncertain fetal head engagement represents 4% of obstetrical situations associated with an increased risk of postpartum hemorrhage, notably in cases of cesarean delivery and increased neonatal impairment owing to failed vaginal instrumental delivery. In this obstetrical condition, cesarean delivery is recommended, but vaginal delivery is possible in two-thirds of the cases. During the second stage of labor, the descent of the fetal head can be assessed by sonography, particularly by measuring the angle of progression.

Objective: To evaluate, after a prolonged second stage of labor, the impact of measuring the angle of progression in addition to a digital examination on cesarean delivery rates when fetal head engagement remains uncertain.

Study design: This open multicenter randomized pragmatic trial included women at term with a singleton cephalic fetus in a clinical occiput anterior position after a prolonged 2-hour second stage of labor with uncertain fetal head engagement. After inclusion in the study, an independent investigator performed ultrasound systematically to confirm the occiput anterior position and measured the angle of progression at the climax of Valsalva pushing. This operator did not participate in labor management. In the study group but not in the control group, the angle of progression was communicated to the obstetrician in charge of labor management. Obstetricians were encouraged to attempt vaginal birth if the angle of progression was >120°. The primary outcome was the cesarean delivery rate. Secondary outcomes were operative delivery rate (cesarean delivery and operative vaginal delivery), maternal complications (third and fourth-degree perineal tears, failed vaginal instrumental delivery, postpartum hemorrhage, hysterectomy), and neonatal outcomes (Apgar score <5 at 10 minutes, umbilical arterial pH <7.10, neonatal wounds, neonatal intensive care unit admission).

Results: A total of 45 women were included in the study. Occiput anterior position was confirmed in 33 women: 16 in the study group and 17 in the control group. Women's characteristics at baseline were similar between the groups. The median (range) angles of progression were similar: 138.4° (15) and 140.3° (16.9) in the study and control group, respectively. Cesarean delivery rates were 12.5% in the study group and 41.1% in the control group (P=.06). Secondary outcomes were similar between the 2 groups. No failed vaginal instrumental delivery was reported.

Conclusion: Measurement of the angle of progression in addition to digital examination when fetal head engagement remained uncertain showed promising results in decreasing cesarean delivery rates. A larger multicenter randomized controlled trial is needed to confirm these results.

Trial registration: ClinicalTrials.gov NCT02761304.

Keywords: angle of progression; cesarean delivery; second stage of labor; transperineal ultrasound.