Preliminary study of fetal head engagement diagnosis by transperineal ultrasound before operative vaginal delivery]

Estimate the predictive value of perineum-fetal head distance obtained by transperineal ultrasound on results of an operative vaginal delivery.A prospective preliminary monocentric study has been conducted on 28 patients between the 18th of April and the 31st of July 2011. Three successive perineum-fetal head distance have been measured before realization of an operative vaginal delivery.With caesarian section deliveries, average distances were higher than with successful operative vaginal deliveries but this result was not significant (49.3mm vs 39.7 mm; P=NS). Ultrasound measured distance was significantly correlated to the time of application of the instrument (r=0.45, P=0.0165). Beyond 50mm, the relative risk of caesarian was 10.5 (IC [0.76-145.36]). The measures were corresponding, with an average time of realization of 29.9 seconds. The transvaginal examination compared to ultrasound showed a discordance of 3.6% for the diagnosis of engagement and of 25% for the descent of fetal head.A larger study is necessary to confirm this result and to recommend the realization of a transperineal ultrasound before an operative vaginal delivery in cases of doubt about engagement after the transvaginal examination.