A uterine fibroid is a noncancerous growth of the muscle tissue in the wall of the uterus. These tumors, also called leiomyomas or myomas, vary in size and number and are common in women of reproductive age. Many fibroids cause no symptoms, but larger or strategically located fibroids can lead to heavy or prolonged menstrual bleeding, pelvic pressure or pain, frequent urination, back or leg pain, and sometimes complications with fertility or pregnancy. The exact cause is not fully understood, though hormonal factors, particularly estrogen and progesterone, as well as genetic predisposition, play a role. Uterine fibroids are generally benign, but monitoring is important when symptoms are present.