Title: P17.08: Can intrapartum ultrasound assessment of fetal spine and head position predict persistent occiput posterior position at delivery?
Abstract: To investigate the predictive values of fetal spine and head position in first and second stage of labour measured by intrapartum ultrasound for persistent occiput posterior position at delivery in Chinese women in Hong Kong. This was a prospective cohort study. 100 women with singleton term pregnancies in cephalic presentation were recruited during first or second stage of labour. They underwent intrapartum transabdominal ultrasound. Fetal spine and head positions were measured. Fetal head positions at birth were recorded. 94 women were studied after excluding 6 women whom were delivered by lower segment Caesarean section in first stage. 35 and 51 women were assessed in first and second stage of labour respectively. 8 women were assessed in both stages. For those assessed in first stage, 9 out of 43 fetuses had occiput posterior position, but only 1 remained in occiput posterior position at delivery. For those assessed in second stage, 9 out of 59 fetuses had occiput posterior position. 7 of them also had spine posterior position. But, only 2 fetuses with both spines and occiputs at posterior position were delivered at occiput posterior position. Sensitivity of using either fetal spine or head position in second stage to predict persistent occiput posterior position at delivery was 66.7%. Specificity of fetal spine position in second stage was 89.3% and specificity of fetal head position was 87.5%. Positive predictive value of fetal spine and head position were 25% and 22.2% respectively, while negative predictive value of both fetal spine and head position were 98%. Positive likelihood ratio (LR+) and negative likelihood ratio (LR-) of fetal spine position were 6.23 and 0.37 respectively. LR+ of fetal head position was 5.34 and LR- was 0.38. Fetal spine and head position in second stage of labour could be helpful for predicting persistent occiput posterior position at delivery. This clinical information could be useful to predict whether the delivery would be successful or not.