GENETIC TESTING

Genetic testing (PGD) is done to determine if one or both parents may have abnormal genes that may increase the chance that their child will have a specific genetic disease.

If the abnormal gene is passed to the child, the child will usually not be affected with that genetic disease but will also be a carrier for that genetic disease. If both parents are carriers of the abnormal gene for the same genetic disease, there is a 25% chance that their child will inherit one abnormal gene from each parent and be affected with that genetic disease. Genetic screening is typically done on one parent first, and if the first parent tests positive, then the other parent is tested. The American College of Obstetricians and Gynecologists (ACOG) recommends screening for certain genetic diseases when indicated due to ethnicity, family history, or other known risk factors.

There are other genetic diseases which are transmitted directly from parent to child, so that if the parent is determined to have the gene causing that genetic disease, there is a 50% risk of the child being affected by the same genetic disease. Certain genetic diseases that are carried on the sex-determining (X & Y) chromosomes may cause disease primarily in male children but only rarely in female children.

During the course of your evaluation and treatment at CTTBC, our experts may recommend screening for specific genetic disease(s) which may be indicated based on your medical history and/or family history, to determine whether or not you are a carrier for the specified genetic disease(s).

Genetic testing is a valuable tool but there are limitations:

  • Negative result – The genetic testing laboratory usually tests for the most common mutations (change in gene structure) and may not identify the less common mutations. So it is possible to have a negative test result but still have a genetic mutation that was not or could not be identified by the testing laboratory due to limitations of current technology.
  • Positive result - A positive test result indicates that you are a carrier for a genetic mutation that can cause a specific genetic disease or can put you and/or your child at risk for developing a disease. If you are determined to be a carrier, your reproductive partner will then be advised to undergo genetic carrier testing.
  • Inconclusive result – Sometimes it is not possible for the testing laboratory to determine genetic mutations. In this case, the genetic carrier test may need to be performed again at the same or different testing laboratory.

This information is provided for general education purposes and is not intended to take the place of a discussion with your physician. If you have questions about any aspect of your health, you are advised to speak with your physician.