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Hydatidiform Mole

(Gestational Trophoblastic Disease; Molar Pregnancy)


Pedro T. Ramirez

, MD, The University of Texas MD Anderson Cancer Center;

Gloria Salvo

, MD, MD Anderson Cancer Center

Last full review/revision Sep 2020

A hydatidiform mole is growth of an abnormal fertilized egg or an overgrowth of tissue from the placenta.

  • Women appear to be pregnant, but the uterus enlarges much more rapidly than in a normal pregnancy.

  • Most women have severe nausea and vomiting, vaginal bleeding, and very high blood pressure.

  • Ultrasonography, blood tests to measure human chorionic gonadotropin (which is produced early during pregnancy), and a biopsy are done.

  • Moles are removed using dilation and curettage (D and C) with suction.

  • If the disorder persists, chemotherapy is needed.

Most often, a hydatidiform mole is an abnormal fertilized egg that develops into a hydatidiform mole rather than a fetus (a condition called molar pregnancy). However, a hydatidiform mole can develop from cells that remain in the uterus after a miscarriage Miscarriage A miscarriage is the loss of a fetus due to natural causes before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect)... read more , a full-term pregnancy, or a mislocated pregnancy ( ectopic pregnancy Ectopic Pregnancy Ectopic pregnancy is attachment (implantation) of a fertilized egg in an abnormal location. In an ectopic pregnancy, the fetus cannot survive. When an ectopic pregnancy ruptures, women often... read more ). Rarely, a hydatidiform mole develops when there is a living fetus. In such cases, the fetus typically dies, and a miscarriage often occurs.

Hydatidiform moles are most common among women under 17 or over 35. In the United States, they occur in about 1 in 2,000 pregnancies. For unknown reasons, hydatidiform moles are almost 10 times more common in Asian countries.

Hydatidiform moles are a type of gestational trophoblastic disease.

Did You Know...

  • An abnormal fertilized egg or abnormal placental tissue can overgrow, causing symptoms similar to those of pregnancy, but the abdomen becomes larger more rapidly.

Types of gestational trophoblastic disease

Gestational trophoblastic disease is a group of disorders that develop from cells (called trophoblasts) that surround a developing embryo Development of the Embryo A baby goes through several stages of development, beginning as a fertilized egg. The egg develops into a blastocyst, an embryo, then a fetus. During each normal menstrual cycle, one egg (ovum)... read more Development of the Embryo and that eventually form the placenta and amniotic sac. The affected cells grow abnormally and multiply quickly.

Gestational trophoblastic disease includes

  • Tumors that do not invade other tissues: These tumors include hydatidiform mole, exaggerated placental site, and placental site nodule. These tumors are usually not cancerous, but they may develop into invasive tumors.

  • Tumors that invade other tissues: These tumors (called gestational trophoblastic neoplasms) include placental-site trophoblastic tumor, epithelioid trophoblastic tumor, choriocarcinoma, and invasive mole. These tumors are usually cancerous.

About 80% of hydatidiform moles are not cancerous.

The rest tend to persist and start to invade surrounding tissue. Most of these moles become invasive moles. About 2 to 3% of hydatidiform moles develop into choriocarcinomas. Choriocarcinomas can spread quickly through the lymphatic vessels or bloodstream.

Placental-site trophoblastic tumors and epithelioid trophoblastic tumors are very rare.

Symptoms of Hydatidiform Mole

Women who have a hydatidiform mole feel as if they are pregnant. But because hydatidiform moles grow much faster than a fetus, the abdomen becomes larger much faster than it does in a normal pregnancy. Severe nausea and vomiting and vaginal bleeding are common. As parts of the mole deteriorate, small amounts of tissue, which resemble a bunch of grapes, may pass through the vagina. These symptoms indicate the need for prompt evaluation by a doctor.

Hydatidiform moles can cause serious complications, including the following:

If choriocarcinoma develops, women may have other symptoms, caused by spread (metastasis) to other parts of the body.

An overactive thyroid gland ( hyperthyroidism Hyperthyroidism Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more Hyperthyroidism ) can occur in women with gestational trophoblastic disease. Symptoms can include an abnormally fast heart rate (tachycardia), warm skin, sweating, heat intolerance, and mild tremors.

Diagnosis of Hydatidiform Mole

  • Blood tests

  • Ultrasonography

  • Biopsy

Often, doctors can diagnose a hydatidiform mole shortly after it forms. They suspect a hydatidiform mole based on symptoms, such as a uterus that is much larger than expected and a vaginal discharge of grapelike tissue.

A pregnancy test is done. If women have a hydatidiform mole, results are positive, but no fetal movement and no fetal heartbeat are detected.

Blood tests to measure the level of human chorionic gonadotropin (hCG—a hormone normally produced early in pregnancy) are done. If a hydatidiform mole or another type of gestational trophoblastic disease is present, the level is usually very high because these tumors produce a large amount of this hormone.

If the level of hCG is very high, doctors do blood tests to check thyroid function and determine whether hyperthyroidism is present.

Ultrasonography is done to be sure that the growth is a hydatidiform mole and not a fetus or amniotic sac (which contains the fetus and fluid around it).

If gestational trophoblastic disease is diagnosed, tests are done to find out if the tumor has spread from where it started to other parts of the body (staging).


Doctors stage gestational trophoblastic neoplasia (the form of gestational trophoblastic disease that is usually cancerous) based on how far it has spread:

  • Stage I: The tumor is only in the uterus.

  • Stage II: The tumor has spread outside the ovary, fallopian tube, vagina, and/or ligaments that support the uterus.

  • Stage III: The tumor has spread to the lungs.

  • Stage IV: The tumor has spread to more distant sites, such as the brain, liver, kidneys, and/or digestive tract.

Prognosis of Hydatidiform Mole

With treatment, many women are cured. The likelihood of cure depends on whether the mole has spread and other factors:

  • If the mole has not spread: Virtually 100%

  • If the mole has spread but is considered low risk: 90 to 95%

  • If the choriocarcinoma has spread widely and is considered high risk: 60 to 80%

Most women who have had a hydatidiform mole can have children afterward and do not have a higher risk of a miscarriage, complications during pregnancy, or children with birth defects.

About 1% of women who have had a hydatidiform mole have another one. So if women have had a hydatidiform mole, ultrasonography is done early in subsequent pregnancies.

Treatment of Hydatidiform Mole

  • Removal of the mole

  • Tests to check for recurrence and/or spread

  • If needed, chemotherapy

A hydatidiform mole or any type of gestational trophoblastic neoplasia is completely removed, usually by D and C with suction. Removal of the uterus ( hysterectomy Hysterectomy Cancer of the uterus develops in the lining of the uterus (endometrium) and is thus also called endometrial cancer. Endometrial cancer usually affects women after menopause. It sometimes causes... read more Hysterectomy ) is rarely necessary but may be done if women do not plan to have children.

Tests to determine whether women need additional treatment are done after the mole is removed.

A chest x-ray is taken to see whether the mole has spread to the lungs.

The level of human chorionic gonadotropin in the blood is measured to determine whether the hydatidiform mole was completely removed. When removal is complete, the level returns to normal, usually within 10 weeks, and remains normal, and no further treatment is needed. If the level does not return to normal, the disease is considered persistent. Then, computed tomography (CT) of the brain, chest, abdomen, and pelvis is done to determine whether choriocarcinoma has developed and spread.

Chemotherapy is needed if the mole persists or has spread but is considered low risk. Chemotherapy may consist of only one drug (methotrexate or dactinomycin). If this treatment is ineffective, a combination of chemotherapy drugs (such as etoposide, methotrexate, dactinomycin, cyclophosphamide, and vincristine) may be used, or hysterectomy may be done.

If the mole has spread widely and is considered high risk, several chemotherapy drugs (usually etoposide, methotrexate, dactinomycin, cyclophosphamide, and vincristine) are used.

Women who have had a hydatidiform mole removed are advised not to become pregnant for 6 months. Oral contraceptives Oral Contraceptives Contraceptive hormones can be Taken by mouth (oral contraceptives) Inserted into the vagina (vaginal rings) Applied to the skin (patch) Implanted under the skin read more Oral Contraceptives are frequently recommended, but other effective contraceptive methods can be used. Pregnancy is delayed so that doctors can make sure that treatment was successful.

If women who have had a hydatidiform mole become pregnant, doctors do ultrasonography early in the pregnancy to determine whether the pregnancy is normal. After the baby is delivered, doctors usually send the placenta to a laboratory to be checked for abnormalities.

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

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