Digital vaginal and ultrasound assessments and the likelihood of intrapartum cesarean delivery: a prognostic factor study.

PURPOSE: Ultrasound offers an objective method of assessing the progress of labour. We sought to examine whether repeat clinical and ultrasound assessments in labour were prognostic for mode of delivery. MATERIALS AND METHODS: Term nulliparous women underwent ultrasound of fetal head position, head descent measured as head-perineum distance, caput succedaneum, moulding, umbilical and middle cerebral artery Doppler and assessment of cervical dilatation from digital vaginal examination. Univariable and multivariable logistic regression analyses were used to investigate a prognostic model for intrapartum Caesarean delivery. RESULTS: Of 270 participants, 269 were evaluable of whom 219 (81%) had repeat ultrasound and clinical assessments; intrapartum Caesarean delivery was required in 79 (29%). The most important parameters to determine the likelihood of intrapartum Caesarean delivery from initial assessment were head station (adjusted odds ratio (AOR) 1.08 per mm, 95% CI 1.04-1.13, p<0.0001) and cervical dilatation (AOR 0.78 per cm, (95% CI 0.66-0.92, p=0.0025). For repeat assessments, cervical dilatation change per hour was most important (AOR 0.10 per cm, (95% CI 0.03-0.26, p<0.0001). Multivariable analysis of initial assessment including gestational age, head descent, cervical dilatation and caput succedaneum gave an area under the curve of 0.72 and 0.78 when cervical dilatation and caput succedaneum were included. CONCLUSION: This study identifies the key parameters associated with mode of delivery in labour, Clinical assessment of cervical dilatation and ultrasound measured head station at initial assessment are most promising prognostic parameters for intrapartum Caesarean delivery. Repeat assessment including change in cervical dilatation improved the prediction to a level that is potentially clinically useful.