Preconception Genetic Carrier Testing
Posted on: June 16, 2017
Preconception genetic carrier screening can determine your risk of passing a genetic disorder to your children.
What is a Carrier?
Many genetic disorders recessive traits, meaning that they are caused when someone inherits two abnormal or mutated copies of a gene- one from each parent. Individuals with one copy of the mutated gene are considered carriers and are typically healthy and have no idea they carry a mutation. There is a 25% chance that two carriers –if they carry mutations in the same gene- will produce a child with that genetic disorder. When one parent has two disorder-causing genes and the other is a carrier, there is a 50% chance of having a child with genetic disorder. There is also a chance that your children will be healthy carriers -like yourself. This 50% risk in offspring also exists for known dominant traits, in which only one copy of the mutated gene is enough to cause the disease.
What is Preconception Genetic Carrier Screening?
Many couples will elect to undergo preconception genetic carrier screening to identify disorder-causing genes and calculate the likelihood of passing these genes to your children before trying to conceive. Using a blood, saliva or a tissue sample- your fertility specialist will look for any genes known to cause genetic disorders. The test will come back as positive (a disorder causing gene exists) or negative (a gene does not exist).
If the partner with a higher risk of being a carrier comes back negative, no further testing is needed. In the event the results are positive, the other partner should also undergo preconception genetic carrier screening. You may be considered higher risk based on your family or ethnic history. Some genetic disorders are more prevalent in people of certain ethnicities.
What Types of Genetic Disorders can be Tested?
While there are not tests for all genetic disorders, you may test for diseases, such as:
- Sickle-cell disease – Most common in African-Americans, sickle-cell disease causes red blood cells to be shaped like crescents, or half-moons. This can lead to chronic anemia and painful episodes.
- Cystic fibrosis – A disease that causes mucus build-up in organs, such as the lungs and pancreas. This can lead to respiratory problems and, eventually, failure. In addition, cystic fibrosis can limit the body’s ability to absorb nutrients.
- Tay-Sachs disease – A disorder most common among people of Eastern and Central European Jewish, Cajun, and French Canadian descent- Tay-Sachs disease causes significant intellectual and physical impairments- usually resulting in death by age 5.
Privacy and Next Steps
Preconception genetic carrier screening is completely voluntary. If you and your partner choose to opt for these tests, the results are protected under the Genetic Information Nondiscrimination Act (GINA). It is illegal for most employers and health insurers to require disclosure of this information for decision-making purposes.
If your results are positive, your fertility specialist can discuss your risks and options. You may choose to become pregnant and have genetic tests done to determine whether or not the fetus has inherited the disorder. In vitro fertilization (IVF) can be performed to allow embryo biopsy for genetic testing to determine whether or not the embryo has inherited the abnormal genes. IVF can also be done with donor eggs or sperm to eliminate the risk of passing that gene to your children.
Whatever your decision, you may wish to tell family members of your findings so that they may chose to undergo testing for themselves. Your fertility specialist or genetic counselor can help if you choose to have this conversation