Descent of fetal head during active pushing: secondary analysis of prospective cohort study investigating ultrasound examination before operative vaginal delivery

Abstract

OBJECTIVES: To investigate if descent of the fetal head during active pushing was associated with duration of operative vaginal delivery, delivery mode and neonatal outcome in nulliparous women with prolonged second stage of labor. METHODS: We conducted a prospective cohort study between November 2013 and July 2016 in five European countries. Fetal head descent was measured with transperineal ultrasound. Head-perineum distance (HPD) was measured between contractions and at maximum contraction during active pushing, and the difference was calculated as delta-HPD. The main outcome was duration of operative vaginal delivery estimated with survival analyses as hazard rations (HRs) for a vaginal delivery, and values >1 show shorter duration. We differentiated delta-HPD into quartiles and compared delivery mode and neonatal outcome between groups. RESULTS: The study population comprised 204 women. Duration of vacuum extraction was shorter with increasing delta-HPD. Estimated mean duration was 10.0, 9.0, 8.8 and 7.5 minutes in quartile 1-4, and the adjusted hazard ratio for vaginal delivery using increasing delta-HPD as continuous variable was 1.04 (95% CI 1.01-1.08). Mean delta-HPD was 7 mm (-10 to 37). Delta-HPD was either negative or ≤2 mm in the lowest quartile. Overall, 7/50 (14%) were delivered with cesarean section in this group compared to 8/154 (5%) if delta-HPD was >2 mm (p <0.05). There was no significant association between umbilical artery pH or Apgar score <7 and delta-HPD groups. CONCLUSION: Lack of fetal head descent during active pushing was associated with longer duration of operative vaginal delivery and higher frequency of cesarean section.