Incidence of Fibroids

Uterine leiomyomas: Causes and incidence

The cause of uterine leiomyomas is unknown, but steroid hormones, including estrogen and progesterone, and several growth factors, including epidermal growth factor, have been implicated as regulators of leiomyoma growth. Leiomyomas typically arise after menarche and regress after menopause, implicating estrogen as a promoter of leiomyoma growth.

Fibroids are extremely common.

Uterine leiomyomas occur in 20% to 25% of women of reproductive age.One study found fibroids, some as small as ¼ inch, in 77% of women. Because ultrasound cannot see these small fibroids we often underestimate how common this condition is. Small fibroids, however, are almost never bothersome. The tumors become malignant (leiomyosarcoma) in only 0.1% or less of patients.

Fibroids can grow in different parts of the uterus. They are named according to which part of the uterus they are found .