Understanding Molar Pregnancy – What the Terms Mean

Hydatidiform Mole and Gestational Trophoblastic Disease

Pregnancy Ultra-sound
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Molar pregnancy and, more generally, gestational trophoblastic tumors or disease can be a scary thing, and it can be even scarier if you have one and then end up hearing a lot of technical terms that you don’t understand. Here’s a quick rundown of what you need to now about the terms behind molar pregnancy and GTTs.

  • Gestational Trophoblastic Disease
    Gestational trophoblastic disease (GTD) is a term used to describe a group of conditions that are characterized by abnormal growth of placental type tissue. There are five types of gestational trophoblastic disease. Two are benign and three are considered malignant. A small percentage of women with benign gestational trophoblastic disease will develop a malignant form of GTD.

  • Hydatidiform Mole (Molar Pregnancy)
    This term refers to the two types of benign GTD which are complete moles and partial moles. Molar pregnancies result from specific chromosomal abnormalities that happen at the time of fertilization.

  • Complete Hydatidiform Mole
    Complete hydatidiform molar pregnancies result from a sperm fertilizing an "empty" egg. A complete hydatidiform mole has no fetal tissue and is the more likely of the two types of molar pregnancies to progress into malignant gestational trophoblastic disease.

  • Partial Hydatidiform Mole
    A partial hydatidiform mole occurs when two sperm fertilize a single egg. The resulting pregnancy might develop a baby, even with a heartbeat, but the pregnancy isn't viable -- the chromosomal abnormalities are incompatible with life. Partial molar pregnancy usually does not cause further complications after treatment.

  • Invasive Mole
    An invasive mole is a hydatidiform mole has penetrated the wall of the uterus and may spread to the rest of the body.

  • Choriocarcinoma
    Choriocarcinoma is a type of cancer that can occur in the uterine lining after a molar pregnancy; most but not all cases of choriocarcinoma are related to molar pregnancy. (Choriocarcinoma can occur after any pregnancy -- even a full-term, normal birth.)

  • Placental Site Trophoblastic Tumors
    This is a form of GTD in which a malignant tumor develops at the former site of a placenta in the uterus. It can occur after any pregnancy but is extremely rare.

    Treatment Molar Pregnancy and Gestational Trophoblastic Tumors

    In the United States, general trophoblastic tumors (GTTs) account for nearly 1 percent of all gynecology malignancies. Fortunately, these tumors are often curable with appropriate treatment and after treatment a patient's fertility is often preserved. Even the most advanced cases of GTT are often curable with the right treatment. Any woman with a GTT must receive individual consideration and treatment by a multidisciplinary specialist group.

    Here are some factors that influence the prognosis of GTT:

    • extent of the disease
    • tumor cell (histological) type
    • disease duration
    • nature of previous pregnancy and any previous treatments for GTT
    • human gonadotropin (HG) titer (HG is a pregnancy hormone)

    Many people with GTT end up needing surgery. However, if a woman has already had a family and no longer wants to have any more children, a hysterectomy is performed. Furthermore, chemotherapy is sometimes given to people with GTT.


    American Cancer Society, “What Is Gestational Trophoblastic Disease?Detailed Guide: Gestational Trophoblastic Disease May 2006. Accessed 26 Jan 2008.

    American Pregnancy Association, “Molar Pregnancy.” Mar 2006. Accessed 26 Jan 2008.

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