Fig. 2.

Reproduced from reference [59]. The level of the cross-section through the fetal head for correct measurement (A). The image (B) is well magnified, the head is horizontal, oval in shape and symmetrical. The landmarks are seen with a centrally positioned and continuous midline falx cerebri (1), the midline echo is broken anteriorly at one-third of its length by the cavum septi pellucidi (2) and the thalami are located symmetrically (3). Callipers, are placed so that their intersection is on the outer border of the bones (C). When using the ellipse facility this should run along the outer border of the skull (D).