Uterine fibroids are very common. The main risk factors are age, hormones and genetics.

Age: It is known that the incidence and severity of fibroids increase with a woman's age. Although some women develop fibroids in their 20's, the majority of women who develop fibroids are in their 30's or 40's.

Hormones: Fibroids tend to shrink after menopause, probably due to the lower levels of estrogen in post-menopausal women. Likewise, fibroids can increase in size during pregnancy due to the higher levels of estrogen in a woman's body.

Genetics: There is a much higher incidence of fibroids among African-American women, which appears to be a genetic factor. However, more research needs to be done to understand this genetic link.