Uterine fibroids are non-cancerous tumours that grow from the muscle layers of the womb. They are medically termed as leiomyomas and myomas. Fibroids are usually tumours of smooth muscle cells and fibrous connective tissue that develop in the uterus. It is estimated that 70-80% of women will develop fibroids in their lifetime.The cause of uterine fibroids is not known.