Assessment of fetal head engagement with transperineal ultrasound: Searching for the cutoff level

In this series, the HPD cutoff distinguishing between engagement and non-engagement was 57mm. Below this cutoff level, the head should be considered engaged, beyond non-engaged. Nevertheless, the pertinence of this cutoff level is hampered by the imprecision of the gold standard used for the clinical diagnosis (transvaginal digital examination). In case of doubt, we recommend, in addition to considering the obstetrical setting, to combine transperineal ultrasound with transvaginal digital examination to avoid deleterious failure of operative vaginal delivery.