Uterine Fibroids

Uterine fibroids are tumors or growths, made up of muscle cells and other tissues that grow within the wall of the uterus (or womb). Although fibroids are sometimes called tumors, they are almost always benign (not cancerous). The medical term for fibroids is uterine leiomyomata (pronounced you-ter-in lie-oh-my-oh-mah-tah). Fibroids can grow as a single growth or in clusters (or groups). Their size can vary from small, like an apple seed (or less than one inch), to even larger than a grapefruit, or eight inches across or more.

Most of the time, fibroids grow in women of childbearing age. While no one knows for sure what will increase a woman's chances of getting fibroids, researchers have found that African American women are 2 to 3 times more likely to get them than women of other racial groups are. African American women also tend to get fibroids at a younger age than do other women with fibroids. Women who are overweight or obese also are at a slightly higher risk for fibroids than women who are not overweight. Women who have given birth appear to be at a lower risk for fibroids. Research is now being done to figure out who is at risk for fibroids.

Fibroids are almost always benign, or not cancerous, and they rarely turn into cancer (less than 0.1 percent of cases). Having fibroids does not increase a woman's chances of getting cancer of the uterus.

Health care providers put fibroids into three groups based on where they grow, such as just underneath the lining of the uterus, in between the muscles of the uterus, or on the outside of the uterus. Most fibroids grow within the wall of the uterus. Some fibroids grow on stalks (called peduncles) that grow out from the surface of the uterus, or into the cavity of the uterus.