USI is caused by weakened pelvic muscles. Pregnancy, childbirth, and repetitive straining or damage to your muscles can lead to permanent weakening. Loss of estrogen at menopause may also play a role, since estrogen helps keep the pelvic muscles strong.

Two factors, working alone or in combination, can lead to urinary stress incontinence. Your doctor may refer to the causes of USI by their technical names:

• Hypermobility of the bladder neck and urethra.
• Intrinsic sphincter deficiency.

Hypermobility of the bladder neck and urethra means that your bladder and urethra have dropped down from their normal positions. With this condition, the sudden, added pressure from coughing, sneezing, or lifting can be enough to cause leaking.

Intrinsic sphincter deficiency is defined as a sphincter that does not close the urethra completely. The sphincter is a muscles, it can become weak or be damaged by such things as trauma, radiation, or surgery.

Loss of the female hormone estrogen at menopause can also play a part by causing thinning of the urethra's inner walls, which can result in an ineffective seal.