The pelvic outlet is described by a line going from the bottom of the pubic bone to the tip of the sacrum.
The pelvic inlet is described by a line going from the top of the pubic bone to the top of the sacrum. While the lowest part of the mother’s spine, the sacrum makes up the back (posterior) wall. Viewing the fetus and the maternal pelvis in a cross-sectional view from the mother’s right side, the front (also known as the anterior) border of the birth canal is provided by the mother’s pubic bone. To better understand the significance of the cardinal movements, let’s do a brief review of maternal pelvic anatomy. The cardinal movements in labor are so named because they are considered essential to successful navigation by the fetus of the maternal birth canal. Cal Shipley with a review of the seven cardinal movements in labor.
