The urethra under stress.

A transient increase in abdominal pressure should be communicated equally to the bladder and urethra. However if the urethra has been moved outside the abdominal cavity by childbirth its ability to respond may well be diminished. A negative closure pressure can then be created and the potential for stress incontinence exists. Hence the voluntary muscles of the levator ani (pelvic floor) are more crucial in providing continence in the female.