Hydatid mole

Hydatid mole


A hydatidiform mole is a rare mass or growth that forms inside the uterus at the beginning of a pregnancy.

See also: Choriocarcinoma

Alternative Names

Hydatid mole; Molar pregnancy


A hydatidiform mole 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. Often, there is no fetus at all.

The cause is not completely understood. Potential causes may include defects in the egg, problems within the uterus, or nutritional deficiencies. Women under 20 or over 40 years of age have a higher risk. Other risk factors may include diets low in protein, folic acid, and carotene.


  • Vaginal bleeding in pregnancy during the first trimester
  • Nausea and vomiting, may be severe enough to require a hospital stay
  • Abnormal growth in the size of the uterus for the stage of the pregnancy
    • Excessive growth in about 50% of cases
    • Smaller-than-expected growth in about 33% of cases
  • Symptoms of hyperthyroidism
    • Rapid heart rate
    • Restlessness, nervousness
    • Heat intolerance
    • Unexplained weight loss
    • Loose stools
    • Trembling hands
    • Skin warmer and more moist than usual
  • Symptoms similar to preeclampsia that occur in the 1st trimester or early 2nd trimester. (This almost always indicates hydatidiform mole, because preeclampsia is extremely rare this early in normal pregnancies.)
    • High blood pressure
    • Swelling in feet, ankles, legs
    • Proteinuria

Exams and Tests

A pelvic examination may show signs similar to a normal pregnancy, but the uterine size may be abnormal and fetal heart sounds are absent. There may be some vaginal bleeding.

Tests may include:

  • Serum HCG
  • Ultrasound of the pelvis
  • Chest x-ray
  • Abdominal CT or MRI

This disease may also affect the results of the following tests:

  • Transvaginal ultrasound
  • HCG (quantitative)


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.

Outlook (Prognosis)

More than 80% of hydatidiform moles are benign (non-cancerous). 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 10-15% of 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, spreading form of cancer. For treatment and outlook information for this condition, see choriocarcinoma

Possible Complications

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


Adequate nutrition may reduce the risk.

Hydatid mole
Aquarium granuloma
Erythroblastosis fetalis
Epidemic arthritic erythema
Adolescent pregnancy
Peritonitis - secondary
Abortion - elective or therapeutic
Erythema multiforme

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