Women's Health Matters

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Fibroids are benign tumours, which grow on the outside, inside or within the smooth muscle in the wall of the uterus. They are not cancers. In very rare cases, a rapidly growing fibroid may become cancerous. This happens to one in a thousand pre-menopausal women, although the risk rises to one in a hundred for women diagnosed with rapidly growing fibroids after menopause.

Fibroids are very common. Approximately 30 percent of women have fibroids large enough to cause symptoms. Some studies suggest that many more women have fibroids but most fibroids do not cause symptoms.

Fibroids that remain small may never require treatment. Since the female hormone estrogen appears to encourage their growth, fibroids usually shrink at menopause and rarely cause problems after this time.

We do not understand why fibroids occur. Women whose close female relatives have fibroids are more likely to develop symptoms, suggesting that the cause is partly genetic. Fibroids are also much more common among African-Canadian women – as many as 50 percent of African American women over the age of 35 have fibroids.


The two most common symptoms of fibroids are:

  1. Heavy Menstrual Bleeding
    A menstrual period typically lasts four or five days. Women with fibroids often have longer periods, which may last seven or more days. These periods may be unusually heavy, sometimes requiring a woman to change her pad or tampon hourly. In addition to the inconvenience, heavy bleeding may also cause anemia and fatigue. Bleeding between periods is not usually a sign of fibroids; however, women who experience this problem should check with their doctor.
  2. Pressure in the Pelvis
    When a fibroid grows large, it can cause a feeling of pressure in the pelvis. It is sometimes possible to feel a hard spot where large fibroids are present. Large fibroids distort the shape of the uterus and cause it to press on other organs. This pressure may cause:
  • frequent urination
  • pain during intercourse
  • constipation
  • abdominal bloating
  • abdominal pain and/or back ache


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  • A publication of:
  • Women's College Hospital