LAUSR

BACKGROUND The diagnosis of labor dystocia is generally determined by the deviation of labor progress, which is assessed by the use of partogram. Recently, intrapartum transperineal ultrasound for the assessment of fetal head descent has been introduced to assess labor progress in the first stage of labor in a more objective and non-invasive way. OBJECTIVE The objective of the study was to determine the differences in labor progress by the use of serial transperineal ultrasound assessment of fetal head descent between women having vaginal and Cesarean delivery. MATERIALS AND METHODS This was a prospective longitudinal study performed in 315 women with singleton pregnancy undergoing labor induction at term between December 2016 and December 2017. Paired assessment of cervical dilatation and fetal head station by vaginal examination and transperineal ultrasonographic assessment of para-sagittal angle of progression and head-perineum distance were made serially following the commencement of labor induction. According to the hospital protocol, assessment was performed every 24 and four hourly, respectively, during latent and active phases of labor. The researchers and the clinical team were blinded to each other's findings. The repeated measures data were analyzed by mixed effect models. To determine the effect of mode of delivery on the association between para-sagittal angle of progression and head-perineum distance against fetal head station and cervical dilatation, the significance of the interaction term between each mode of delivery and fetal head station or cervical dilatation was determined, accounting for parity and obesity. Area under receiver-operating characteristic curve (AUROC) was used to evaluate the performance of serial intrapartum sonography in predicting women with Cesarean delivery due to failure to progress. RESULTS The total number of paired vaginal examination and ultrasound assessments was 1,198 with a median of three per woman. The median assessment-to-assessment interval was 4.6 hours (interquartile range 4.3-5.1). Women achieving vaginal delivery (n=261) had steeper slopes of para-sagittal angle of progression and head-perineum distance against fetal head station and cervical dilatation than those achieving Cesarean delivery (n=54). Objectively, an additional decrease of 5.11° and 1.37° in para-sagittal angle of progression was observed for an unit increase in fetal head station and cervical dilatation, respectively, in women requiring Cesarean delivery (p<0.01; p=0.01), compared to women achieving vaginal delivery, after taking account of repeated measures from individuals and confounding factors. The respective additional increase in head-perineum distance for an unit increase in fetal head station and cervical dilatation were 0.27 cm (p<0.01) and 0.12 cm (p<0.01). A combination of maternal characteristics with the temporal changes of para-sagittal angle of progression for an unit increase in fetal head station achieved an AUROC of 0.85 (95% confidence interval: 0.76-0.94), with sensitivity of 79% and specificity of 80%, for the prediction of women requiring Cesarean delivery due to failure to progress. CONCLUSION The differences in labor progress between vaginal and Cesarean delivery have been illustrated objectively by serial intrapartum transperineal ultrasonographic assessment of fetal head descent. This tool is potentially predictive of women requiring Cesarean delivery due to failure to progress.