What causes abnormal uterine bleeding?

In many women, a hormone imbalance causes bleeding. These women may have too much estrogen or not enough progesterone. Polyps or fibroids (small and large growths) in the uterus can also cause bleeding. Cancer of the uterus and infection of the cervix are other causes of bleeding. Sometimes a thyroid problem causes bleeding.

These are just a few of the problems that can cause abnormal uterine bleeding. These problems can occur at any age. But the likely cause of abnormal uterine bleeding depends on your age.

Women in their 20s and 30s:

A common cause of abnormal bleeding in young women and teenagers is pregnancy. Many women have bleeding in the first few months of a normal pregnancy. Birth control pills or the Norplant birth control device can also cause abnormal bleeding. If an egg isn't released (ovulation) during your menstrual cycle, you might have abnormal bleeding—either light spotting between periods or heavy bleeding during your period.

Women in their 40s and early 50s:

In the years before menopause, women have months when they don't ovulate. This can cause abnormal uterine bleeding. Thickening of the lining of the uterus (called the endometrium) is another cause of bleeding in women in their 40s. This thickening can be a warning of uterine cancer. In women in their 40s and early 50s, it's important to make sure uterine cancer isn't the cause of abnormal bleeding.

Women after menopause:

Hormone replacement therapy is often a cause of uterine bleeding after menopause. Other causes include a thickened endometrium and uterine cancer. Uterine cancer is more common in older women than in younger women. But cancer is not always the cause of abnormal uterine bleeding. Many other problems can cause bleeding after menopause.

What tests can find the cause of abnormal uterine bleeding?

The tests your doctor orders may depend on your age. If you could be pregnant, your doctor may order a pregnancy test. If your bleeding is heavy, your doctor may want to check your blood count to make sure you don't have anemia (low iron) from the blood loss.

An ultrasound exam of your uterus shows both the uterus and the ovaries. It may also show the cause of your bleeding.

Your doctor may want to do an endometrial biopsy. This is a test of the uterine lining. It's done by putting a thin plastic tube (called a catheter) into your uterus. A tiny piece of the uterine lining is taken out and sent to a lab. The biopsy will show if you have cancer or a change in the cells. This test can be done in the doctor's office and causes only mild pain.

Another test is a hysteroscopy. A thin tube with a tiny camera in it is put into your uterus. The camera lets your doctor see the inside of your uterus. If anything abnormal shows up, your doctor can get a biopsy.

Will I need a D&C?

A D&C is a short name for dilatation and curettage. Whether you need to have one depends on your problem. When you have a D&C, the opening of your cervix is stretched just enough so a surgical tool can be put into your uterus. The tool is used to scrape away the lining of your uterus. The removed lining is checked in a lab for abnormal tissue. A D&C is done under anesthesia, while you're “asleep.”

If you're having heavy bleeding, a D&C may be done both to find out the problem and to treat the bleeding. A D&C often makes heavy bleeding stop.

How is abnormal uterine bleeding treated?

The treatment depends on the cause. If the cause is a hormone imbalance, your doctor may suggest you take birth control pills or progesterone. If the bleeding is related to hormone replacement therapy, your doctor may change the amount of estrogen you take. If a thyroid problem is causing your bleeding, treatment of that problem itself may stop the bleeding. You may need surgery if you have endometrial hyperplasia or cancer.