The pelvic canal

The circular space enclosed by the pubic bones at the front, and the ischium on either side at the back, is called the pelvic canal (the bony passage through which the baby must pass).

The size and shape of the pelvis are important for labour and delivery. Well-built healthy women, who had a good diet during their childhood growth period, usually have a broad pelvis that is well adapted for childbirth. It has a round pelvic brim and short; blunt ischial spines called a "gynaecoid" pelvis. In a more detailed context, the pelvis has inlet and outlet.

The pelvic inlet - the pelvic inlet is formed by the pelvic brim. The pelvic brim is rounded, except where the sacral promontory and the ischial spines project into it. The dimensions in centimetres (cm) of the pelvic inlet are shown in Figure 1.4 in both directions (top to bottom; and transverse or side to side).

The pelvic outlet: the pelvic outlet is formed by the lower border of the pubic bones at the front, and the lower border of the sacrum at the back. The ischial spines point into this space on both sides. Figure 1.5 shows the dimensions of the space that the foetus must pass through as it emerges from the mother's pelvis.