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    Molar Pregnancy - Topic Overview

    What is a molar pregnancy?

    A molar pregnancy happens when tissue that normally becomes a fetus instead becomes an abnormal growth in your uterus. Even though it isn't an embryo, this growth triggers symptoms of pregnancy.

    A molar pregnancy should be treated right away. This will make sure that all of the tissue is removed. This tissue can cause serious problems in some women.

    About 1 out of 1,500 women with early pregnancy symptoms has a molar pregnancy.

    What causes a molar pregnancy?

    Molar pregnancy is thought to be caused by a problem with the genetic information of an egg or sperm. There are two types of molar pregnancy: complete and partial.

    • Complete molar pregnancy. An egg with no genetic information is fertilized by a sperm. It does not develop into a fetus but continues to grow as a lump of abnormal tissue that looks a bit like a cluster of grapes and can fill the uterus.
    • Partial molar pregnancy. An egg is fertilized by two sperm. The placenta becomes the molar growth. Any fetal tissue that forms is likely to have severe defects.

    Sometimes a pregnancy that seems to be twins is found to be one fetus and one molar pregnancy. But this is very rare.

    Things that may increase your risk of having a molar pregnancy include:

    • Age. The risk for complete molar pregnancy steadily increases after age 35.
    • A history of molar pregnancy, especially if you've had two or more.
    • A history of miscarriage.
    • A diet low in carotene. Carotene is a form of vitamin A. Women who don't get enough of this vitamin have a higher rate of complete molar pregnancy.

    What are the symptoms?

    A molar pregnancy causes the same early symptoms that a normal pregnancy does, such as a missed period or morning sickness. But a molar pregnancy usually causes other symptoms too. These may include:

    Most of these symptoms can also occur with a normal pregnancy, a multiple pregnancy, or a miscarriage.

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