Uterine fibroids are noncancerous growths of the uterus that always appear during childbearing years. Also called leiomyoma’s (lie-o-my-O-muhs) or myomas, uterine fibroids aren’t related to an increased risk of uterine cancer and almost never become cancer.

Fibroids are benign tumors made from smooth muscle cells and fibrous animal tissue. They develop in the uterus. It is estimated that 70-80% of girls will develop fibroids in their lifetime—however, not everyone will develop symptoms or require treatment.

Fibroids are abnormal growths that develop in or on a woman’s uterus. Sometimes these tumors become quite large and cause severe abdominal pain and heavy periods.


Many women who have fibroids do not have any symptoms. Around 1 in 3 women with fibroids will experience symptoms. In women who have symptoms, the foremost common signs and symptoms of uterine fibroids include:

  • Heavy, painful periods, also known as menorrhagia
  • anemia from heavy periods
  • lower backache or leg pain
  • constipation
  • discomfort in the lower abdomen, especially in the case of large fibroids
  • frequent urination
  • pain during intercourse, known as dyspareunia
  • pregnancy problems
  • labor problems

It remains unclear exactly what causes fibroids. They may be related to estrogen levels.

  • Genetic changes
  • Hormones
  • Other growth factors
  • Extracellular matrix (ECM)