Definition of 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:

• Gestational trophoblastic disease
• Choriocarcinoma (a cancerous form of GTD)

Causes, incidence, and risk factors:

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. The exact cause of fertilization problems are unknown. However, a diet low in protein, animal fat, and vitamin A may play a role.

Symptoms:

• Abnormal growth of the womb (uterus)
  • Excessive growth in about half of cases
  • Smaller-than-expected growth in about a third of cases
• Nausea and vomiting that may be severe enough to require a hospital stay
• Vaginal bleeding in pregnancy during the first 3 months of pregnancy
• Symptoms of hyperthyroidism
  • Heat intolerance
  • Loose stools
  • Rapid heart rate
  • Restlessness, nervousness
  • Skin warmer and more moist than usual
  • Trembling hands
  • Unexplained weight loss
• Symptoms similar to preeclampsia that occur in the 1st trimester or early 2nd trimester -- this is almost always a sign of a hydatidiform mole, because preeclampsia is extremely rare this early in a normal pregnancy
  • High blood pressure
  • Swelling in feet, ankles, legs

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:

• HCG blood test
• Chest x-ray
• CT or MRI of the abdomen
• Complete blood count
• Blood clotting tests
• Kidney and liver function tests

Treatment:

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. It is important to avoid pregnancy and to use a reliable contraceptive for 6 - 12 months after treatment for a molar pregnancy. This allows for accurate testing to be sure that the abnormal tissue does not return. Women who get pregnant too soon after a molar pregnancy have a greater risk of having another one.

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

Complications:

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

Other complications related to the surgery to remove a molar pregnancy include:

• Preeclampsia
• Thyroid problems