EP23.16: Prelabour estimations of delivery mode and fetal head engagement in primiparous at term

Clinical lack of fetal head engagement (FHE) in term primiparous has a controversial incidence and has been associated with labour arrest disorders. Our objective was to analyse longitudinally the evolution of fetal head situation at term and the correlations with the delivery mode in primiparous at term. Starting at 37GW we determined weekly in unselected primiparous the occiput position and TPU measurements: progression angle (PA), progression distance (PD), direction angle (DA) and head to perineum distance (HPD). The evolution of these measurements was studied and compared against the station 0 cut-offs from the literature. Maternal and labour characteristics were noted. In 262 studied term primiparous the rates of FHE at any examination at term were between 3.3–5.7% (depending on the TPU measurement). We did not identify a specific trendline for the US measurements at term. Moreover, the differences between vaginal and Caesarean cases were generally not significant. Analysing only the data from the week before delivery WBD, the relation between the US parameters and the delivery mode failed or was only poor (AUC = 0.550 for DA, 0.588 for PA and 0.623 for PD). When considering the occiput position, the analysis performs slightly better, but the correlations remain poor (AUC = 0.584, 0.663, 0.671). Engagement rate at term was lower than any report published so far, but this is the only study that used objective US evaluation. We could not find strong associations between US determinations at term and the delivery mode. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.