Uterine fibroids are benign (noncancerous) tumors that grow on or within the muscle tissue of the uterus. Approximately 20-40% of women 35 years and older have fibroid tumors. Fibroids are more common among women of African-American descent. Some statistics indicate that up to 80% of African-American women will develop uterine fibroids. While some women do not experience any of the symptoms of fibroids, the location and size of fibroid tumors can cause symptoms that can affect a woman's quality of life.

Fibroids are hormonally sensitive so symptoms are likely to be cyclical, like menstruation. As estrogen levels tend to increase prior to the onset of menopause, this may cause the size of many uterine fibroids to increase. This may cause an increase in the symptoms of fibroids as well. During menopause the levels of estrogen decrease dramatically, causing fibroids to shrink. However, women taking hormone replacement therapy (HRT) during menopause may not experience any symptom relief because the estrogen contained in this regime may cause fibroid tumors to enlarge and symptoms to return.

The size of fibroids range from very small (walnut size) to as large as a cantaloupe or even larger. Typically, physicians measure uterine fibroids in terms of the size of the uterus during pregnancy; for example, a very large fibroid can cause the uterus to become the size of a six- or seven-month pregnancy (24-28 weeks). Additionally, there can either be one dominant fibroid or a cluster of many small fibroid tumors.