A uterine fibroid is a non-cancerous tumour that grows in the uterus. They may be single, or multiple, and can be of various sizes and locations. Fibroids range in size from a few millimetres to 10 cm or more – about the size of a grapefruit. There can be many fibroids, causing the uterus to enlarge, in some cases to the size of a full term pregnancy. Fibroids  may grow in the muscle layer of the uterus (intramural), into the uterine cavity (submucosal), or may project outside the uterus (subserosal).

Uterine fibroids are the most common tumour of the female reproductive system, affecting 70-80% of women who have reached the age of 50. They are also more common in women who are very overweight, and in women who have never had children.

It is not uncommon for a woman to be unaware that she has uterine fibroids, and to have them diagnosed at a routine check-up or observed on an ultrasound or other imaging. However, for some women, a variety of symptoms may be experienced.