Uterine fibroids are growths in the uterus . They are not cancer. Fibroids can grow on the inside of the uterus , within the muscle wall of the uterus , or on the outer surface of the uterus . They can change the shape of the uterus as they grow. This can make it hard for you to get pregnant, or it can cause problems during a pregnancy.

Over time, the size, shape, location, and symptoms of fibroids may change.

As women get older, they are more likely to have uterine fibroids, especially from their 30s and 40s until menopause. Most have mild or no symptoms. But fibroids can cause bad pain, bleeding, and other problems.

The cause of fibroids is not known. But the hormones estrogen and progesterone can make them grow. A woman's body makes the highest levels of these hormones during her childbearing years. After menopause, when hormone levels decrease, fibroids often shrink or disappear.

Uterine fibroids usually need treatment when they cause:

• Anemia from heavy fibroid bleeding.
• Ongoing low back pain or a feeling of pressure in the lower belly.
• Trouble getting pregnant.
• Problems during a past pregnancy, such as miscarriage or preterm labor.
• Problems with the urinary tract or bowels.
• Infection, if the tissue of a large fibroid dies.

Depending on the reasons you need treatment, one type of treatment may work better for you than another.

Uterine fibroid embolization is a procedure that blocks blood flow to fibroids in the uterus. It's not surgery. Fibroids treated with this procedure shrink by about half. ^{footnote 2}

The doctor (a radiologist ) puts a thin, flexible tube called a catheter into a blood vessel in your upper thigh (femoral artery). Then the doctor injects a substance called contrast material into the catheter. He or she uses an X-ray on a video screen to see the arteries and guide the catheter to the arteries that supply blood to the fibroid. Small particles are injected into those uterine arteries through the catheter. These particles build up in the arteries and block blood flow to the fibroid. The rest of the uterus usually isn't harmed, because it's supplied by other arteries.

Uterine fibroid embolization can be used to control heavy, long-lasting menstrual bleeding when:

• You have tried hormones, but they didn't relieve your symptoms.
• You don't plan to get pregnant. This treatment is a choice for women who have no plans to get pregnant. That's because some women have had damage to an ovary, have gone into early menopause , or had trouble getting pregnant after the procedure.
• You don't want to have surgery ( myomectomy or hysterectomy). You would need only local anesthesia for this procedure. And the doctor doesn't have to make any cuts in your skin. For most women, this means no hospital stay and a quicker return to normal activities, compared to surgery. ^{footnote 3}
• You have other health problems, such as severe lung or liver disease, that make it risky for you to have surgery or use hormones.

Embolization usually works well to treat fibroids. Short-term studies show that: ^{footnote 1}

• About 80 out of 100 women who had it said that their symptoms got better, while 20 out of 100 said their symptoms didn't get better.
• It shrinks fibroids an average of about 50%. ^{footnote 1}

But the results don't always last: In one study, nearly 1 out of 4 women who had embolization needed another one or a hysterectomy within the next couple of years. ^{footnote 4}

The chance of a problem after embolization is low. But the risks include:

• Infection. This is the most serious possible problem. In rare cases, an emergency hysterectomy is needed to treat an infected uterus.
• Early menopause.
• Scar tissue ( adhesions ).
• Pain that in rare cases could last for months.

Although some women can get pregnant after this procedure, experts don't yet fully know the risks to pregnancy.

If you're thinking of having this procedure, look for a radiologist who has done it many times with few problems.

Your doctor might recommend this procedure if:

• You've tried hormones, and they didn't work for you.
• You have another health problem that makes surgery or hormones too risky.
• You don't plan to get pregnant.