The pelvis protects the reproductive organs, and is the bony passage through which the baby must pass in order to be born.
Consists of four bones:
ONE sacrum (triangular bone with five vertabrae fused together)
ONE coccyx (small bone at the tip of the sacrum) AKA “tailbone”
TWO innominate bones (hip bones on each side)
– Each innominate bone is formed by the fusion of three bones around the acetabulum:
A. Ilium AKA “the hips” is the uppermost pelvic bone.
– Both innominate bones are joined in the back to the sacrum at the sacroiliac synchondroses and in front to one another at the symphysis pubis.
Four joints of the pelvis:
- Pubic symphysis
Flexibility of the Pelvis during Pregnancy and Labor
Progesterone and relaxin make the pelvis joints flexible, letting the pelvis accomodate for the baby to pass through.
- The sacroiliac joints
Increase its diameter during labor.
- The coccyx
Is pushed back while the head descends down to the perineum.
- The symphysis pubis
Increase in width and mobility during pregnancy which returns to normal following delivery.