Engagement is when the fetal head enters into the pelvic inlet (Figure 1.3, diagram 2). The head is said to be engaged when the biparietal diameter (measuring ear tip to ear tip across the top of the babys head, see Figure 1.4 below) descends into the pelvic inlet, and the occiput is at the level of the ischial spines in the mother's pelvis (see Figure 1.5).

Figure 1.4 Moulding of the fetal skull may occur during descent; in this example, one parietal bone is overlapping the other at the sagittal suture. The occiput and the distance known as the bi-parietal diameter have been labelled.

Figure 1.5 The pelvic inlet, viewed from above. Note the position of the ischial spines.
Last modified: Monday, 14 July 2014, 1:00 PM