Someone holding their pelvis.
Uterine fibroids are non-cancerous pelvic tumors.

What Causes Uterine Fibroids

About 70% of women will have uterine fibroids at some time during their life and may not even know it. So, what causes uterine fibroids? You’re about to find out.

What Are Uterine Fibroids?

Uterine fibroids are a type of pelvic tumor. These non-cancerous growths are made of muscle cells and fibrous connective tissue, giving the tumor a firm texture. They range in size from being so tiny you can’t see them with the naked eye to bulky masses that distort the uterus. A woman can have one or multiple uterine fibroids, which can grow at different rates. Uterine fibroids are fairly common and almost always benign, but that doesn’t mean they’re harmless.

The Difference Between a Cyst and a Fibroid

Cysts and fibroids are two different growths inside of a woman’s reproductive system. Cysts are fluid-filled sacs that are generally attached to an ovary—either on the inside or outside. Fibroids are not found within the ovaries; they only grow inside the uterus or on the uterine walls. Unlike the cyst, uterine fibroids are solid, non-cancerous tumors.

Uterine Fibroids and Pregnancy

Uterine fibroids generally show up in the midst of a woman’s childbearing years—usually in her 30s or 40s. Depending on the size, shape, and location of the fibroids, they may block the fallopian tubes, impacting fertility by making it difficult for a woman to conceive.

Causes of Uterine Fibroids

Doctors believe that uterine fibroids grow from a stem cell in the muscular tissue of the uterus, but further research is required. While causes of uterine fibroids remains unknown, there are some possible causes that have been identified. Potential causes may involve:

  • Genetics. Genes that have differences from those in normal uterine muscle cells may play a part in the development of ovarian fibroids.
  • Hormones. Research shows that women in their childbearing years are more likely to get uterine fibroids and fibroids shrink after menopause. Both of these moments in a woman’s lifecycle involve a change in hormones. Estrogen and progesterone appear to encourage fibroid growth since fibroids contain more receptors for these two hormones than normal uterine muscles. In menopause, there is a decrease in hormone production, which explains why uterine fibroids shrink at this stage in life.
  • Extracellular matrix (ECM). ECM makes cells stick to each other. Fibroids have increased ECM, giving them their fibrous quality. ECM is also known to cause biologic changes in cells.

Risk Groups for Uterine Fibroids

There are a few risk categories where uterine fibroids are more common. Risk is increased with:

  • Age: fibroids are more common in women in their childbearing years (usually after 30).
  • Family history: your risk increases if you have an immediate family member (a mother or sister) who has uterine fibroids.
  • Obesity: women who are overweight are at a higher risk.
  • Race: uterine fibroids affect women of all races; however, black women are more likely to have fibroids.
  • Other factors: early menopause, vitamin D deficiency, alcohol consumption, or a diet rich in red meat and low in leafy vegetables, fruit, and dairy.
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What Are the Symptoms?

Uterine fibroids often don’t come with symptoms. Symptoms may appear due to the location, size, and number of fibroids present. There are several symptoms that can be caused by uterine fibroids, including:

  • Period abnormalities, including a heavier or prolonged period or bleeding between periods
  • Severe pelvic pain, pressure, or cramps
  • Protruding belly
  • Difficulty emptying the bladder or frequent urination
  • Pain in the lower back or in the legs
  • Pain during intercourse
  • Difficulty getting pregnant
  • Fatigue caused by anemia
  • Constipation

Treatment Options

The spectrum of recommended treatment for uterine fibroids ranges from no treatment to surgery. Treatment isn’t usually necessary unless the fibroids cause discomfort or other health issues. The recommended treatment will also rely on your age, how many fibroids you have and their size, other health conditions you may have, and other factors.

The Wait and See Approach

Your doctor may start by monitoring the fibroids over time. As women get closer to menopause, most fibroids stop growing and may even shrink, making treatment unnecessary.


Medication is only available to temporarily tackle your symptoms, rather than make the fibroids disappear. Hormonal drugs may help reduce any abnormal bleeding and regulate your menstrual cycle. In very specialized cases, doctors may prescribe GnRH agonists, a drug that blocks the production of estrogen, which temporarily shrinks fibroids and stops heavy bleeding.


This operation removes fibroids but preserves the uterus.


This is another surgical option where the entire uterus, and in some cases one or both ovaries, is removed.

Uterine Artery Embolization (UAE)

An alternative to open surgery, this procedure blocks blood flow to the fibroids. Without a blood supply, the fibroids shrink and die.

Uterine Fibroid Prevention Methods

There isn’t much scientific research available on how to avoid uterine fibroids, which means that prevention may not actually be possible. Some research suggests that using hormonal contraceptives (birth control pills, a hormonal IUD, etc.) may be linked with a lower risk of fibroids. Overall, the best advice out there is to live a healthy lifestyle; make sure to exercise and eat a diet rich in fruits and vegetables.

It may seem a little dark to say that you may have fibroids and not even know it, but it’s true. Uterine fibroids are fairly common and may explain symptoms that you can’t attribute to another medical issue. Since uterine fibroids are often found during a physical exam, it underlines the importance of routine check-ins with your doctor; make time to schedule an appointment.