A rare mass or growth that may form inside the uterus at the beginning of a pregnancy . See also choriocarcinoma .

Alternative Names

Hydatid mole; Molar pregnancy

Causes, incidence, and risk factors

Hydatidiform moles arise from placental and/or fetal tissue and, therefore can only occur in conjunction with the early stages of pregnancy . The mass is usually placental material that grows uncontrolled. Frequently there is no fetus at all. The cause of this developmental disorder is not completely understood. Potential causes may include defects of the ovum (egg), abnormalities within the uterus, and/or nutritional deficiencies. The incidence in the U.S. is 1 out of 1000 pregnancies; however, it occurs in up to 1 out of 125 pregnancies in Mexico and some Asian countries. Women under 20 or over 40 years old have an increased incidence. Risk factors include low socioeconomic status and diets low in protein , folic acid , and carotene .

Signs and tests

A pelvic examination may show signs similar to normal pregnancy except uterine size may be abnormal and some bleeding may be noted. The fundal height measurement is inconsistent for the weeks of pregnancy and fetal heart tones are absent. Tests typically include:

A

serum HCG to confirm pregnancy, then serial HCG (repeated at regular intervals) to monitor the rate and consistency of decline if hydatidiform mole suspected

An ultrasound of the pelvis

A chest X-ray and abdominal CT or MRI will be recommended for some patients

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

Transvaginal ultrasound

HCG (quantitative)

Treatment

If spontaneous

abortion does not occur and the diagnosis is confirmed, therapeutic abortion is performed by suction curettage (D and C). Following either case, serum HCG levels are monitored to assure they return to a normal, non-pregnant level. A hysterectomy may be an option for older women who do not desire future pregnancies.

Expectations (prognosis)

More than 80% of hydatidiform moles are benign . Outcome after treatment is usually excellent. Close follow-up is essential. Highly effective means of contraception are recommended to avoid pregnancy for at least 6 to 12 months. In 10 to 15% of cases, hydatidiform moles may develop into invasive moles. Invasive moles, however, may intrude so far into the uterine wall that hemorrhage or other complications develop. In 2 to 3% of cases, hydatidiform moles may develop into choriocarcinoma , which is a malignant, rapidly- growing, and metastatic (spreading) form of cancer . Despite these factors, the rate of cure after treatment with chemotherapy is high. Over 90% of women with malignant, non-spreading (nonmetastatic) disease are able to preserve reproductive abilities. In those with metastatic disease, remission remains at 75 to 85%.

Complications

Acute pulmonary (lung) insufficiency may develop after evacuation of the uterus in cases where uterine enlargement is greater than 16 weeks gestational size.

Calling your health care provider

Call your health care provider/obstetrician if hydatidiform mole is suspected.

Prevention

Adequate nutrition may decrease risk.