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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).
Hydatid mole; Molar pregnancy
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.
- 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
- 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
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
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.
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.
Other complications related to the surgery to remove a molar pregnancy include:
- Thyroid problems
Calling your health care provider
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.
Goldstein DP, Berkowitz RS. Gestational trophoblastic disease. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKenna WG, eds. Abeloff’s Clinical Oncology. 4th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 94.
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Review Date: 11/21/2010
Review By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; 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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