fibroid fact sheet

about fibroids

Fibroids are muscular lumps (tumor) that grow in the wall of the uterus (womb). Another medical term for fibroids is “leiomyoma” or just “myoma”. Fibroids are almost always benign (not cancerous). Fibroids can grow as a single tumor, or there can be many of them in the uterus. They can be as small as an apple seed or as big as a grapefruit. In unusual cases they can become very large.


About 20 to 80 percent of women develop fibroids by the time they reach age 50. Fibroids are most common in women in their 40s and early 50s. Not all women with fibroids have symptoms. Women who do have symptoms often find fibroids hard to live with. Some have pain and heavy menstrual bleeding. Fibroids also can put pressure on the bladder, causing frequent urination, or the rectum, causing rectal pressure.

who gets fibroids?

Fibroids become more common as women age, especially during the menopause. After menopause, fibroids usually shrink.

  • If a woman’s mother had fibroids, her risk of having them is about three times higher than average.
  • African-American women are more likely to develop fibroids than white women.
  • Women who are overweight are at higher risk for fibroids.


Most fibroids grow in the wall of the uterus. Doctors put them into three groups based on where they grow:

  • Submucosal: fibroids grow into the uterine cavity.
  • Intramural fibroids grow within the wall of the uterus.
  • Subserosal: fibroids grow on the outside of the uterus.
  • Pedunculated: Some fibroids grow on stalks that grow out from the surface of the uterus or into the cavity of the uterus. They might look like mushrooms.


Most fibroids do not cause any symptoms, but some women with fibroids can have:

  • Heavy bleeding (which can be heavy enough to cause anemia) or painful periods
  • Feeling of fullness in the pelvic area (lower stomach area)
  • Enlargement of the lower abdomen
  • Frequent urination
  • Pain during sex
  • Lower back pain
  • Reproductive problems, such as infertility, which is very rare


No one knows for sure what causes fibroids. Researchers think they may be Hormonal or Genetic (runs in families).

Because no one knows for sure, we also don’t know what causes them to grow or shrink. We do know that they are under hormonal control — both estrogen and progesterone. They grow rapidly during pregnancy, when hormone levels are high. They shrink when anti-hormone medication is used. They also stop growing or shrink once a woman reaches menopause.


Fibroids are almost always NOT cancerous (they are benign). Rarely does a cancerous fibroid occur. This is called leiomyosarcoma. Doctors think that these cancers do not arise from an already-existing fibroid. Having fibroids does not increase the risk of developing a cancerous fibroid. Having fibroids also does not increase a woman’s chances of getting other forms of cancer in the uterus.


Most women with fibroids have normal pregnancies but are more likely to have problems during pregnancy and delivery.

The risk of needing a caesarian section is six times greater for women with fibroids.

The risk of placental abruption, where the placenta breaks away from the wall of the uterus before delivery is increased.

All obstetricians have experience dealing with fibroids and pregnancy. Most women who have fibroids and become pregnant do not need to see an OB who deals with high-risk pregnancies.

diagnosis & treatment

Sometimes your doctor can feel the fibroid as a (usually painless) lump or mass on the uterus.

Ultrasound is commonly used to diagnose fibroids.

If you have fibroids but do not have any symptoms, you may not need treatment. Your doctor will check during your regular exams to see if they have grown.

If necessary, fibroids can be treated surgically or with medications.