Topic Overview

What is a molar pregnancy?

A molar pregnancy happens when tissue that normally becomes a fetus instead becomes an abnormal growth in your uterus. Even though it isn’t an embryo, this growth triggers symptoms of pregnancy.

A molar pregnancy should be treated right away. This will make sure that all of the tissue is removed. This tissue can cause serious problems in some women.

About 1 out of 1,500 women with early pregnancy symptoms has a molar pregnancy.

What causes a molar pregnancy?

Molar pregnancy is thought to be caused by a problem with the genetic information of an egg or sperm. There are two types of molar pregnancy: complete and partial.

• Complete molar pregnancy. An egg with no genetic information is fertilized by a sperm. It does not develop into a fetus but continues to grow as a lump of abnormal tissue that looks a bit like a cluster of grapes and can fill the uterus.
• Partial molar pregnancy. An egg is fertilized by two sperm. The placenta becomes the molar growth. Any fetal tissue that forms is likely to have severe defects.

Sometimes a pregnancy that seems to be twins is found to be one fetus and one molar pregnancy. But this is very rare.

Things that may increase your risk of having a molar pregnancy include:

• Age. The risk for complete molar pregnancy steadily increases after age 35.
• A history of molar pregnancy, especially if you’ve had two or more.
• A history of miscarriage.
• A diet low in folic acid or carotene. Carotene is a form of vitamin A. Women who don’t get enough of these vitamins have a higher rate of complete molar pregnancy.

What are the symptoms?

A molar pregnancy causes the same early symptoms that a normal pregnancy does, such as a missed period or morning sickness. But a molar pregnancy usually causes other symptoms too. These may include:

• Bleeding from the vagina.
• A uterus that is larger than normal.
• Severe nausea and vomiting.
• Signs of hyperthyroidism. These include feeling nervous or tired, having a fast or irregular heartbeat, and sweating a lot.
• An uncomfortable feeling in the pelvis.
• Vaginal discharge of tissue that is shaped like grapes. This is usually a sign of molar pregnancy.

Most of these symptoms can also occur with a normal pregnancy, a multiple pregnancy, or a miscarriage.

How is a molar pregnancy diagnosed?

Your doctor can confirm a molar pregnancy with:

• A blood test to measure your pregnancy hormones.
• A pelvic ultrasound.

Your doctor can also find a molar pregnancy during a routine ultrasound in early pregnancy. Partial molar pregnancies are often found when a woman is treated for an incomplete miscarriage.

What are the risks of having a molar pregnancy?

A molar pregnancy can cause heavy bleeding from the uterus.

Some molar pregnancies lead to gestational trophoblastic disease, a growth of abnormal tissue inside the uterus. Sometimes this tissue keeps growing after the molar pregnancy is removed.

• Complete molar pregnancies: Out of 1000 cases of complete molar pregnancy, 150 to 200 develop trophoblastic disease that keeps growing after the tissue is removed. This means that in the other 800 to 850 cases, this doesn’t happen.
• Partial molar pregnancies: Out of 1000 cases of partial molar pregnancy, about 50 develop trophoblastic disease. This means that in 950 cases out of 1000, this doesn’t happen.

In a few cases, trophoblastic disease turns into cancer. In rare cases, the abnormal tissue can spread to other parts of the body.

Almost all women who get this cancer are cured with treatment.

How is it treated?

When you have a molar pregnancy, you need treatment right away to remove all of the growth from your uterus. The growth is removed with a procedure called vacuum aspiration.

If you are done having children, you may decide to have your uterus removed (hysterectomy) instead of having a vacuum aspiration to treat your molar pregnancy.

After treatment, you will have regular blood tests to look for signs of trophoblastic disease. These blood tests will be done over the next 6 to 12 months. If you still have your uterus, you will need to use birth control for the next 6 to 12 months so you don’t get pregnant. It is very important to see your doctor for all follow-up visits.

If you do get trophoblastic disease, there’s a small chance that it will turn into cancer. But your doctor will likely find it early so it can be cured with chemotherapy. In the rare case when the cancer has had time to spread to other parts of the body, more chemotherapy is needed, sometimes combined with radiation treatment.

Trophoblastic disease doesn’t keep most women from becoming pregnant later.

After a molar pregnancy, you may feel very sad and worry about cancer. It may help to find a local support group or talk to your friends, a counselor, or a religious adviser.