What Are Uterine Fibroids?

Fibroids are the most frequently seen tumors of the female reproductive system. Fibroids, also known as uterine myomas, leiomyomas, or fibromas, are firm, compact tumors that are made of smooth muscle cells and fibrous connective tissue that develop in the uterus. It is estimated that between 20 to 50 percent of women of reproductive age have fibroids, although not all are diagnosed. Some estimates state that up to 30 to 77 percent of women will develop fibroids sometime during their childbearing years, although only about one-third of these fibroids are large enough to be detected by a health care provider during a physical examination.

In more than 99 percent of fibroid cases, the tumors are benign (non-cancerous). These tumors are not associated with cancer and do not increase a woman’s risk for uterine cancer. They may range in size, from the size of a pea to the size of a softball or small grapefruit.