my info says:
the pelvic floor is a group of muscles that form the floor of the pelvis in a sling like arrangement attatching the back sides and front of the pelvis and the surrounding openings of the V, bladder, uterus and bowel. their function is to support the pelvic organs and control bladder and bowel. during pregnancy these can become very stretched and weak so need regular exercising.
Exercise helps to strengthen the muscles providfing good support of the pelvic organs, improving bladder control, and maintaining sexual satisfaction from good muscle tone.
Hope that explains for you