A uterine fibroid is a non-cancerous (benign) tumor that originates from the smooth muscle layer (myometrium) and the accompanying connective tissue of the uterus. Fibroids are the most common benign tumors in females and typically found during the middle and later reproductive years. While most fibroids are asymptomatic, they can grow and cause heavy and painful menstruation, painful sexual intercourse, and urinary frequency and urgency. Uterine fibroids are the major indication for hysterectomy in the US. Fibroids are often multiple and if the uterus contains too many leiomyomatas to count, it is referred to as uterine leiomyomatosis. The malignant version of a fibroid is uncommon and termed a leiomyosarcoma.