Molar Pregnancy

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Molar Pregnancy

Topic Overview

What is a molar pregnancy?

A molar pregnancy happens when tissue that normally becomes a fetus instead becomes a growth, called a mole, in your uterus. Even though it is not an embryo, a mole triggers symptoms of pregnancy.

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

About 1 out of 1,000 women with early pregnancy symptoms has a molar pregnancy.1 This means that 999 women out of 1,000 do not have this problem.

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. The sperm grows on its own, but it can only become a lump of tissue. It cannot become a fetus. As this tissue grows, it looks a bit like a cluster of grapes. This cluster of tissue is called a mole, and it can fill the uterus.
  • Partial molar pregnancy. An egg is fertilized by two sperm. The placenta grows into a mole. 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 mole. But this is very rare.2

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

  • Age. The risk for complete molar pregnancy steadily increases after age 35.3
  • A history of molar pregnancy, especially if you've had two or more.4
  • A history of miscarriage.
  • A diet low in carotene. Carotene is a form of vitamin A. Women who don't get enough of this vitamin have a higher rate of complete molar pregnancy.3

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 pelvic examination.
  • 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. Sometimes this disease keeps growing after the mole is removed.

  • Complete molar pregnancies: Out of 1000 cases of complete molar pregnancy, 150 to 200 develop trophoblastic disease that keeps growing after the mole is removed.4 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.4 This means that in 950 cases out of 1000, this doesn't happen.

In a few cases, trophoblastic disease turns into cancer. Fortunately, almost all women who get this cancer are cured with treatment.1

In rare cases, the abnormal tissue can spread to other parts of the body.

How is it treated?

When you have a molar pregnancy, you need treatment right away to remove all the growth from your uterus. Then 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 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, additional chemotherapy is needed, sometimes combined with radiation treatment.

Trophoblastic disease doesn't keep most women from becoming pregnant later.3

After a molar pregnancy, it’s normal to feel very sad and to worry about cancer. It may help to find a local support group or talk to your friends, a counsellor, or a religious adviser.

Frequently Asked Questions

Learning about molar pregnancy:

Being diagnosed:

Getting treatment:

Ongoing concerns:


A molar pregnancy typically triggers common signs of pregnancy, such as a missed menstrual period, breast tenderness, fatigue, increased urination, and morning sickness.

Contact your doctor immediately if you have signs of pregnancy and if you have any of the following during your first trimester:

  • Vaginal discharge of tissue that is shaped like grapes. This is the most characteristic symptom of a molar pregnancy.
  • Vaginal bleeding (light or heavy). Light vaginal bleeding in the first trimester is common in a normal pregnancy. But it may signal a molar pregnancy or a miscarriage.
  • Severe nausea and vomiting. These symptoms occur sometimes in a molar pregnancy.
  • Signs of hyperthyroidism, such as fatigue, weight loss, increased heart rate, heat intolerance, sweating, irritability, anxiety, muscle weakness, and thyroid enlargement.

Signs of a molar pregnancy that your doctor might find during an examination include:

  • High blood pressure, which is a common symptom of pre-eclampsia. A molar pregnancy can cause pre-eclampsia to develop during the first or early second trimester.
  • No fetal heartbeat. No fetus is present in complete molar pregnancies and in some partial molar pregnancies.
  • A uterus that is abnormally large for the length of the pregnancy. There are reasons other than a molar pregnancy for a large uterus, such as being pregnant with twins or not knowing how long you have been pregnant. But an abnormally large uterus is a common sign of molar pregnancy.

Complete molar pregnancies are now often diagnosed by ultrasound earlier in pregnancy than they were in the past. So women with complete molar pregnancies seldom have the condition long enough to have symptoms such as excessive uterine size, nausea, vomiting, pre-eclampsia, and hyperthyroidism.

Examinations and Tests

Most molar pregnancies are identified when they are still small. If you have symptoms that suggest a molar pregnancy, see your doctor immediately. You will be evaluated with a simple examination and tests, including:

  • A pelvic examination, to evaluate the size of the uterus and check for abnormalities.
  • A blood test to measure the amount of a pregnancy hormone, called human chorionic gonadotropin (hCG), to see whether the level is abnormally high for the length of the pregnancy.
  • A pelvic ultrasound test. If a pelvic examination or hCG level suggests a molar pregnancy, an ultrasound can be used to confirm the diagnosis. Some molar pregnancies are first diagnosed during an ultrasound done for another purpose.

If you are diagnosed with a molar pregnancy, blood and urine tests and chest X-ray may be done to check for:

Treatment Overview

A molar pregnancy is removed with vacuum aspiration under general anesthesia. Pelvic ultrasound may be used during the procedure to guide removal of all the abnormal tissue. Medicine (oxytocin) is used during or after the procedure to make the uterus contract. Uterine contractions help the uterus shrink to its pre-pregnancy size and help stop uterine bleeding after the mole is removed.

If you have Rh-negative blood, you will also have a shot of Rh immune globulin. This prevents a problem called Rh sensitization, which can cause serious problems in a future pregnancy.

If you have no future plans to become pregnant, you may consider a hysterectomy, which reduces the chance of having gestational trophoblastic disease after a molar pregnancy.

If you are considered high risk for cancer after a molar pregnancy, you may be treated with methotrexate to prevent persistent cell growth.

In the very rare case that a normal fetus is present along with a mole, the fetus is watched closely and delivered as soon as possible.

Important follow-up care

If you have had a molar pregnancy, it is important to see your doctor for routine follow-up visits to watch for any cancerous cell growth. Follow-up includes:

  • Measuring hCG levels every 1 to 2 weeks until they are normal, then measuring them every 1 to 2 months for 6 months to a year. Levels of hCG that stay high may be a sign of cancer.
  • Preventing pregnancy while hCG levels are being monitored, usually about 6 months. It is very important that you practice highly effective birth control during the entire period of follow-up. For more information on contraception, see the topic Birth Control.
  • Close medical supervision if you happen to conceive within 12 months of molar pregnancy treatment.

You will likely be referred to an obstetrician, a gynecologist, or a doctor specializing in reproductive cancer (gynecologic oncologist) to treat a molar pregnancy.

If you are diagnosed with trophoblastic cancer

Most cases of trophoblastic cancer are confined to the uterus. If you are diagnosed with this low-risk and highly curable type of cancer, you will probably receive one or more series of a medicine, either methotrexate or actinomycin D.

If you are diagnosed with cancer that has spread to other parts of the body, you will probably be treated with a combination of chemotherapy medicines.

Fertility and coping after a molar pregnancy

After a molar pregnancy, your chances of having a successful pregnancy are about the same as those of the general population of child-bearing women, even if you have been treated for trophoblastic disease. But you do have an increased risk for having another molar pregnancy. So your doctor will want to watch you closely during and after any future pregnancies. Pregnancy care will include:

  • Routine prenatal care and a late first-trimester fetal ultrasound to confirm a healthy pregnancy.
  • Checking hCG levels 6 weeks after childbirth to confirm that no trophoblastic disease has developed.

Having a molar pregnancy can challenge your emotional and physical well-being. Grief about losing a pregnancy, combined with fear of cancer, may feel like more than you can handle. Consider contacting a support group or talking to friends, a counsellor, or a member of the clergy to help you and your family deal with this difficult time. For more information, see the topic Grief and Grieving.

Home Treatment

There is no home treatment for a molar pregnancy.

If you have had a molar pregnancy, use highly effective birth control measures to prevent pregnancy during the 6 to 12 months following treatment, according to your doctor's advice. For more information on contraception, see the topic Birth Control.

Other Places To Get Help


Society of Obstetricians and Gynaecologists of Canada (SOGC)
780 Echo Drive
Ottawa, ON  K1S 5R7
Phone: 1-800-561-2416
(613) 730-4192
Fax: (613) 730-4314
Web Address:

The mission of SOGC is to promote optimal women's health through leadership, collaboration, education, research, and advocacy in the practise of obstetrics and gynaecology.

Canadian Cancer Society
10 Alcorn Avenue
Suite 200
Toronto, ON  M4V 3B1
Phone: (416) 961-7223
Fax: (416) 961-4189
Web Address:

The Canadian Cancer Society (CCS) is a national, community-based organization that provides information about cancer prevention, care, and treatment. The CCS also provides funding for cancer research.

March of Dimes
1275 Mamaroneck Avenue
White Plains, NY  10605
Phone: (914) 997-4488
Web Address:

The March of Dimes tries to improve the health of babies by preventing birth defects, premature birth, and early death. March of Dimes supports research, community services, education, and advocacy to save babies' lives. The organization's Web site has information on premature birth, birth defects, birth defects testing, pregnancy, and prenatal care. You can sign up to get a free newsletter and also explore Understanding Your Newborn: An Interactive Program for New Parents.

U.S. National Cancer Institute (NCI)
6116 Executive Boulevard
Suite 300
Bethesda, MD  20892-8322
Phone: 1-800-4-CANCER (1-800-422-6237)
TDD: 1-800-332-8615
Web Address: (or for live help online)

The U.S. National Cancer Institute (NCI) is a U.S. government agency that provides up-to-date information about the prevention, detection, and treatment of cancer. NCI also offers supportive care to people with cancer and to their families. NCI information is also available to doctors, nurses, and other health professionals. NCI provides the latest information about clinical trials. The Cancer Information Service, a service of NCI, has trained staff members available to answer questions and send free publications. Spanish-speaking staff members are also available.



  1. Cunningham FG, et al. (2005). Gestational trophoblastic disease. In Williams Obstetrics, 22nd ed., pp. 273–284. New York: McGraw-Hill.
  2. Wax JR, et al. (2003). Prenatal diagnosis by DNA polymorphism analysis of complete mole with coexisting twin. American Journal of Obstetrics and Gynecology, 188: 1105–1106.
  3. Berkowitz RS, Goldstein DP (2007). Gestational trophoblastic disease. In JS Berek, ed., Berek and Novak's Gynecology, 14th ed., pp. 1581–1603. Philadelphia: Lippincott Williams and Wilkins.
  4. Burtness B (2004). Neoplastic diseases. In G Burrow et al., eds., Medical Complications During Pregnancy, 6th ed., pp. 479–504. Philadelphia: Elsevier.

Other Works Consulted

  • Aghajanian P (2007). Gestational trophoblastic diseases. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., pp. 885–895. New York: McGraw-Hill.
  • Li AJ (2008). Gestational trophoblastic neoplasms. In RS Gibbs et al., eds. Danforth's Obstetrics and Gynecology, 10th ed., pp. 1073–1085. Philadelphia: Lippincott Williams and Wilkins.


By Healthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Specialist Medical Reviewer Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology
Last Revised January 26, 2010

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