The female bony pelvis is an important consideration in childbirth.
Several studies have been concerned with the spatial relationships of the female bony pelvis. One of the most extensive is the Caldwell-Moloy Classification of Female Pelvis.
This study categorizes female pelvis by shape. It illustrates those types that are better and those that are less well suited for childbirth.
Just before childbirth, the phenomenon of "relaxation" occurs. In this phenomenon, the ligaments of the bony pelvis and perineum become quite stretchable.
This increases the diameters of the birth canal.