Prediction of delivery mode by ultrasound-assessed fetal position in nulliparous women with prolonged first stage of labor.

Abstract

To ascertain if fetal head position on transabdominal ultrasound is associated with delivery by Cesarean section in nulliparous women with a prolonged first stage of labor. This was a prospective observational study performed at Stavanger University Hospital, Norway, and Addenbrooke's Hospital, Cambridge, UK, between January 2012 and April 2013. Nulliparous pregnant women with a singleton cephalic presentation at term and prolonged labor had fetal head position assessed by ultrasound. The main outcome was Cesarean section vs vaginal delivery, and secondary outcomes were association of fetal head position with operative vaginal delivery and duration of remaining time in labor. Fetal head position was assessed successfully by ultrasound examination in 142/150 (95%) women. In total, 19/50 (38%) women with a fetus in the occiput posterior (OP) position were delivered by Cesarean section compared with 16/92 (17%) women with a fetus in a non-OP position (P = 0.01). On multivariable logistic regression analysis, the OP position predicted delivery by Cesarean section with an odds ratio (OR) of 2.9 (95% CI, 1.3-6.7; P = 0.01) and induction of labor with an OR of 2.4 (95% CI, 1.0-5.6; P = 0.05). Fetal head position was not associated with operative vaginal delivery or with remaining time in labor. The agreement between a digital and an ultrasound assessment of OP position was poor (Cohen's kappa = 0.19; P = 0.18). OP fetal head position assessed by transabdominal ultrasound was significantly associated with delivery by Cesarean section.