A double uterus is a rare congenital abnormality. In a female fetus, the uterus starts out as two small tubes. As the fetus develops, the tubes normally join to create one larger, hollow organ — the uterus.

Sometimes, however, the tubes don't join completely. Instead, each one develops into a separate structure. A double uterus may have one opening (cervix) into one vagina, or each uterine cavity may have a cervix. In many cases, a thin wall of tissue runs down the length of the vagina, dividing it into two separate openings.

Women who have a double uterus often have successful pregnancies. But the condition can increase the risk of miscarriage or premature birth.

A double uterus often causes no symptoms. The condition may be discovered during a regular pelvic exam or during imaging tests to determine the cause of repeated miscarriages.

Women who have a double vagina along with a double uterus may initially consult a doctor for menstrual bleeding that isn't stopped by a tampon. In these situations, the woman has placed a tampon in one vagina, but blood is still escaping from the second uterus and vagina.

When to see a doctor

Seek medical advice if you have a menstrual flow despite the insertion of a tampon, or if you have severe pain with menstruation or experience repeated miscarriages.

Doctors aren't certain why some fetuses develop a double uterus and others don't. A genetic component may be a factor because this rare condition sometimes runs in families.

Many women with a double uterus have normal sex lives, pregnancies and deliveries. But sometimes a double uterus and other abnormalities of uterine development are associated with:

• Infertility
• Miscarriage
• Premature birth
• Kidney problems

A double uterus may be diagnosed during a routine pelvic exam when your doctor observes a double cervix or feels an abnormally shaped uterus. To confirm the diagnosis, your doctor may recommend one or more of the following tests:

• Ultrasound. This test uses high-frequency sound waves to create images of the inside of your body. To capture the images, a device called a transducer is either pressed against your abdominal skin or inserted into your vagina (transvaginal ultrasound). Both types of ultrasound may be done to get the best view. A 3-D ultrasound may be used where available.
• Sonohysterogram. The sonohysterogram (son-o-HIS-ter-o-gram), an ultrasound scan, is done after fluid is injected through a tube into your uterus by way of your vagina and cervix. This allows your doctor to look for problems in the shape of your uterus.
• Magnetic resonance imaging (MRI). The MRI machine looks like a tunnel that has both ends open. You lie down on a movable table that slides into the opening of the tunnel. This painless procedure uses a magnetic field and radio waves to create cross-sectional images of the inside of your body.
• Hysterosalpingography. During a hysterosalpingography (his-tur-o-sal-ping-GOG-ruh-fe), a special dye is injected into your uterus through your cervix. As the dye moves through your reproductive organs, X-rays are taken to determine the shape and size of your uterus and whether your fallopian tubes are open.

If you have a double uterus but you don't have signs or symptoms, treatment is rarely needed. Surgery to unite a double uterus is rarely done — although surgery may help you keep a pregnancy if you have a partial division within your uterus and no other medical explanation for a previous pregnancy loss.

If you have a double vagina in addition to a double uterus, you might be a candidate for an operation that would remove the wall of tissue separating the two vaginas. This can make childbirth a little easier.

You're likely to start by seeing your primary care provider. You might be referred to a doctor who specializes in conditions affecting the female reproductive tract (gynecologist) or a doctor who specializes in reproductive hormones and optimizing fertility (reproductive endocrinologist).

What you can do

To prepare for your appointment:

• Ask if there's anything you need to do in advance to prepare for any possible tests.
• Make a list of any menstrual symptoms you've had and for how long.
• Make a list of your key medical information, including any other conditions for which you're being treated and the names of any medications, vitamins, herbs or supplements you're taking.
• Take a family member or friend along, if possible, to help you remember everything.
• Make a list of questions to ask your doctor to help you make the most of your visit.

Some basic questions to ask your doctor include:

• What is the most likely cause of my signs and symptoms?
• Are there any other possible causes?
• What treatment approach do you recommend, if any?
• Am I a candidate for surgical treatment? Why or why not?
• Am I at increased risk of problems during pregnancy?
• What options are available to improve my chances of a successful pregnancy, if necessary?
• Should I see a specialist?
• Are there any brochures or other printed materials that I can have? What websites do you recommend?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

• What are your signs and symptoms, and when did you first notice them?
• Are your signs and symptoms continuous, or do they come and go?
• Do you menstruate regularly?
• What is a typical menstrual period like for you?
• Have you ever been pregnant?
• If you have been pregnant, what was the outcome?
• Do you hope to have biological children in the future?
• Are you currently being treated or have you recently been treated for any other medical conditions?