• Risk Factors for Chromosomal Abnormalities

    A risk factor is something that increases your likelihood of getting a disease or condition.
    It is possible to develop a chromosomal abnormality with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of having a baby that develops a chromosomal abnormality. Talk to your doctor about how you can reduce your risk.


    The leading cause of chromosomal abnormality is the mother’s age. The likelihood increases as the mother’s age increase. However, more babies are born to younger women, so more younger women have babies with a chromosomal abnormality. The actual number of chromosomal abnormalities passed on is difficult to determine because most result in miscarriages early in the pregnancy.
    Maternal Age Risk of Any Chromosomal Abnormality Risk of Down’s Syndrome
    15-24 1/500 1/1500
    25-29 1/385 1/1100
    35 1/178 1/350
    40 1/63 1/100
    45 1/18 1/25
    These statistics only account for live births.

    Medical Conditions

    If you have already had a child affected by a chromosomal abnormality, you are at increased risk for passing along another chromosomal abnormality.
    If you and your partner have experienced at least two spontaneous abortions, you should talk to your healthcare provider about conducting an investigation of your chromosomes. This investigation comes back normal 95% of the time. If the results are not normal, you and your partner should meet with a human geneticist since this is an ever changing field.

    Living Environment

    A study published in February 2005, showed that prenatal exposure to combustion-related urban air pollutants alters the structure of chromosomes of babies in the womb. This is the first study to show that environmental exposure during pregnancy to such pollutants can cause a modest but significant increase in chromosomal abnormalities in fetal tissues.


    Chromosomal abnormalities. March of Dimes website. Available at : http://www.marchofdimes.com/professionals/14332%5F1209.asp . Accessed on September 5, 2005.

    Chromosomal abnormalities. The Merck Manual website. Available at: http://www.merck.com/mrkshared/mmanual/section19/chapter261/261l.jsp . Accessed on September 4, 2005.

    Study: prenatal exposure to air pollutants causes genetic alterations. Columbia University website. Available at: http://www.columbia.edu/cu/news/05/02/pollution%5Fpregnacy.html . Accessed September 7, 2005.

    Revision Information

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