Definition of Uterine fibroids:

Uterine fibroids are noncancerous tumors that develop within or attach to the wall of the uterus, a female reproductive organ.

Causes, incidence, and risk factors:

Uterine fibroids are the most common pelvic tumor. Fibroids may be seen as many as 1 in every 5 women in their childbearing years (the time after starting menstruation for the first time and before menopause.)

Fibroids usually affect women over age 30. They are rare in women under 20 or in those who have gone through menopause. They are more common in African-Americans than Caucasians.

The cause of uterine fibroid tumors is unknown. However, fibroid growth seems to depend on the hormone estrogen. As long as a woman with fibroids is menstruating, a fibroid will probably continue to grow, usually slowly.

Fibroids can be so tiny that you need a microscope to see them. However, they can also grow very large. They may fill the entire uterus, and may weigh several pounds. Although it is possible for just one fibroid to develop, usually there is more than one.

Sometimes, a fibroid hangs from a long stalk, which is attached to the outside of the uterus. This is called a pedunculated fibroid.