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    4 Common Causes of Miscarriage

    Now that you're pregnant, you may be concerned about the risks of a miscarriage. Most miscarriages occur for reasons you have no control over. In fact, it's often difficult to pinpoint the exact cause. Learning what causes miscarriage may help put your mind at ease and help you improve your chances for having a healthy, full-term pregnancy.

    Here's an overview of four of the most common causes of miscarriage.

    Cause No. 1: Abnormal Chromosomes

    More than half of miscarriages in the first 13 weeks of pregnancy occur because of a problem with the baby's chromosomes. Chromosomes contain the genes that determine your baby's unique traits, such as hair and eye color. A baby can't grow normally with the wrong number of chromosomes or with damaged ones.

    Here are some other things to keep in mind about abnormal chromosomes:

    • There's no way to prevent chromosome problems from happening.
    • As you get older, especially after age 35, your risk for chromosome problems specifically, and miscarriage in general, increases.

    Miscarriages from chromosome problems usually don't occur again in future pregnancies.

    Cause No. 2: Medical Conditions

    A miscarriage during weeks 13 through 24, the second trimester, often results from a problem with the mother. These are some health problems that increase a woman's risk for miscarriage.

    • An infection such as cytomegalovirus or German measles.
    • Hormone problems that prevent the lining of your uterus from thickening, which the fertilized egg needs to implant.
    • Poorly controlled chronic diseases such as diabetes or high blood pressure.
    • Thyroid disease, lupus, and other autoimmune disorders.
    • Problems with your uterus or cervix, such as: fibroids; an abnormally shaped uterus; or a cervix that opens and widens too early, called incompetent cervix.

    Cause No. 3: Lifestyle

    Your habits as the mom-to-be can increase the risk of miscarriage. Here are some habits that are dangerous for a developing baby:

    • Smoking. Some studies show an increased risk of miscarriage even if only the father smokes.
    • Heavy drinking
    • Using illegal drugs

    Cause No. 4: Environmental Hazards

    In addition to secondhand smoke, certain substances in your environment at home or at work may also put your pregnancy at risk for miscarriage. These include:

    • Lead in old water pipes or paint in homes built before 1978.
    • Mercury released from broken thermometers or fluorescent light bulbs.
    • Solvents such as paint thinners, degreasers, and stain and varnish removers.
    • Pesticides for killing insects or rodents.
    • Arsenic found near waste sites or in some well water.

    Be sure to talk with your doctor about this. You may find your risks are not as great as you think.

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