When the baby's head encounters the muscles of the pelvic floor, the mechanical process of stretching and compressing the nerves to the bladder, urethra and pelvis causes nerve damage. Depending on the size and weight of the baby and length of labor, damage occurs to the soft tissue of the muscle and nerves and may cause tears in ligaments that support the urethra and bladder muscles. As baby's head crowns, the significant downward pressure further stretches the nerves. Episiotomies, anesthesia and the use of forceps all may cause incontinence. Urinary incontinence that begins after delivery usually stops in the next 3-6 months, however, it may recur and persist after additional pregnancies.
Women often report difficulty with contracting their pelvic muscles after childbirth.
It has been suggested that elective cesarean delivery would significantly decrease, but not eliminate, the conditions of pelvic organ prolapse and urinary incontinence. Unlike health care services in countries such as Great Britain and France, the U.S. health care system does not promote pelvic muscle rehabilitation immediately after childbirth, although the data strongly suggests that this is a crucial time when pelvic floor muscle and nerve damage occur. Sampselle, CM, Miller, JM, Mims, BL, Delancey, JOL et al. Effect of Pelvic muscle exercise on transient incontinence during pregnancy and after birth. Menopause is a risk factor for urinary incontinence since decreasing estrogen levels can cause weakness in the bladder, urethra and pelvic muscles.