Ultrasound in labor: is it time for a more simplified approach?

The use of transperineal intrapartum ultrasound assessment has been introduced in recent years to complement traditional digital evaluation, with the aim of providing an objective evaluation of fetal head descent1−5. Despite an increasing number of studies on the subject, the application of this method in everyday clinical practice remains difficult, probably because of the technical difficulty in obtaining most of the sonographic parameters that have been suggested thus far6,7. However, Eggebø et al. have proposed a measurement that is simply obtained, i.e. the distance between the fetal skull and the perineum on transperineal ultrasound (the head–perineum distance (HPD))3 (Figure 1a). More recently we have proposed another simple index of fetal head station inspired by the obstetric literature, i.e. the distance between the lower edge of the maternal symphysis pubis and the fetal skull, along the infrapubic line (the fetal head–symphysis distance (HSD)) (Figure 1b)8.We studied HSD with threedimensional ultrasound which gave us the opportunity to measure both HPD and HSD retrospectively using the volume datasets we had stored (Figure 2).