Expanded Carrier Testing

Expanded carrier screening tests are called “expanded” because they look for an increased risk of more than 100 genetic conditions including Cystic Fibrosis, Tay Sachs and Sickle Cell Disease. They also can detect Fragile X Syndrome, the most common inherited form of intellectual disability and autism, as well as Spinal Muscular Atrophy, the most common cause of death from a recessive genetic disease in infants.

By testing your blood and sometimes your saliva, your doctor can check if you carry genes that could increase your baby’s risk of having a recessive genetic disorder. Expanded carrier screening tests can be performed either before you become pregnant or any time during your pregnancy.

Is Expanded Carrier Screening Right for You?

Like all genetic screening tests, expanded carrier screening tests are optional. You may wish to have this test since the outcome for babies and children with some recessive genetic disorders, such as Wilson Disease (inability to rid the body of excess copper), can be improved if they are treated early. Expanded Carrier Screening poses no risk to the pregnancy and is non-invasive.

Recessive genetic disorders occur when a child inherits two alleles of a gene, one from each parent, that have the same error in the DNA code. It is rare that two people who are carriers of the same genetic disorder come together to become parents, and even when this happens, there is a one in four chance that both alleles with the genetic defect are passed on and result in a genetic disorder. (There is a 50 percent chance the child will be a carrier like his or her parents and a 25 percent chance that the child will not be a carrier at all.)

The odds of you and your partner both being carriers of the same recessively inherited disease go up somewhat if you are genetically related or come from the same ethnic background. Examples of recessive genetic disorders linked with specific ethnic backgrounds include:

• Cystic Fibrosis in Caucasians (whites)
• Sickle cell disease in African-Americans
• Thalassemia in Asians and individuals of Mediterranean descent
• Tay-Sachs in Canavan disease in Ashkenazi Jews

If you have an expanded carrier screening test, remember that this is a screening test to look for an increased risk to see if your baby has a recessive genetic condition. It is not a diagnostic test.

What Happens if You Test Positive

Don’t be alarmed if the test results indicate you have a gene for an inherited disease. This result does not mean that you have that disease or that your baby will develop that disease. For your baby to develop a recessive genetic disorder, both you and your partner must carry the gene for the condition and have transmitted that gene to your baby. One of the few exceptions to this rule is Fragile X Syndrome where the condition can develop with a gene from the mother.

If you and/or your partner test positive for carrying a recessive genetic disorder, we will give you an assessment of your child’s risk of inheriting the condition. We may refer you for additional testing and you may meet with a genetic counselor who can offer detailed, personalized genetic guidance and advice.