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Hydatidiform mole



A hydatidiform mole is a rare mass or growth that forms inside the uterus at the beginning of a pregnancy. It is a type of gestational trophoblastic disease (GTD).

See also:

Alternative Names

Hydatid mole; Molar pregnancy


A hydatidiform mole, or molar pregnancy, results from over-production of the tissue that is supposed to develop into the placenta. The placenta normally feeds a fetus during pregnancy. In this condition, the tissues develop into an abnormal growth, called a mass.

There are two types:

  • Partial molar pregnancy
  • Complete molar pregnancy

A partial molar pregnancy means there is an abnormal placenta and some fetal development.

In a complete molar pregnancy, there is an abnormal placenta but no fetus.

Both forms are due to problems during fertilization. Potential causes may include defects in the egg, problems within the uterus, or a diet low in protein, animal fat, and vitamin A. Women under age 16 or older than 40 have a higher risk for this condition. You also are more likely to have a molar pregnancy if you have had one in the past.

Signs and tests

A pelvic examination may show signs similar to a normal pregnancy, but the size of the womb may be abnormal and the baby's heart sounds are absent. There may be some vaginal bleeding.

A pregnancy ultrasound will show an abnormal placenta with or without some development of a baby.

Tests may include:

Support Groups

Expectations (prognosis)

More than 80% of hydatidiform moles are benign (noncancerous). The outcome after treatment is usually excellent. Close follow-up is essential. After treatment, you should use very effective contraception for at least 6 to 12 months to avoid pregnancy.

In some cases, hydatidiform moles may develop into invasive moles. These moles may grow so far into the uterine wall and cause bleeding or other complications.

In a few cases, a hydatidiform mole may develop into a choriocarcinoma, a fast-growing cancerous form of gestational trophoblastic disease. See: Choriocarcinoma


Lung problems may occur after a D and C if the woman's uterus is bigger than 16 weeks gestational size.


If your doctor suspects a molar pregnancy, a suction curettage (D and C) may be performed.

A hysterectomy may be an option for older women who do not wish to become pregnant in the future.

After treatment, serum HCG levels will be followed.


Kavanagh JJ, Gershenson DM. Gestational trophoblastic disease: hydatidiform mole, nonmetastatic and metastatic gestational trophoblastic tumor: diagnosis and management. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM, eds. Comprehensive Gynecology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2007:chap 35.

Copeland LJ, Landon MB. Malignant diseases and pregnancy. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics - Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2007:chap 45.

Soper J, Creasman WT. Gestational trophoblastic disease. In: DiSaia P, Creasman W, eds. Clinical Gynecologic Oncology. 7th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 7.

Review Date: 10/28/2008
Reviewed By: Linda Vorvick, MD, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine; and Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Redmond, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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