What is carrier screening?
There are a number of inherited conditions which can be screened for in the general population. Genetic screening tests can detect carriers for an inherited condition even though a woman and her partner do not have a family history of the condition. Carrier screening is typically performed for genetic diseases in which both parents must be carriers in order to have an affected child. Carrier screening determines whether or not an individual carries a change in one of their genes and if they are at increased risk of having a child affected with a genetic disease. Everyone carries abnormal genes, and in general, carriers have no symptoms or signs of the disease they carry. It is important to note that you can be a carrier of a genetic disease even if you already have healthy children. Carrier screening typically involves a blood test from one or both parents and can be performed when you are planning pregnancy or after you have become pregnant.
What if we are both carriers?
If you are both carriers of a gene for the same disease there is a 25 percent (1 in 4) chance with any pregnancy of having an affected child. Prenatal diagnosis by chorionic villus sampling and/or amniocentesis can be performed to determine if an unborn baby has inherited the abnormal genes from both parents.
Testing the baby after birth is also an option if a couple does not want prenatal diagnosis.
What does a negative result mean?
A negative result very significantly lowers but does not completely eliminate the risk of being a carrier.
What carrier screening is recommended?
We recommend that all women consider having carrier screening for cystic fibrosis, spinal muscular atrophy (SMA), sickle cell disease and other hemoglobin disorders. A number of genetic disorders occur more frequently in certain ethnic populations. Therefore, your ethnic background and your partner’s ethnic background may be used to determine any additional screening tests that will be offered to you.
Expanded Carrier Screening
Some women may elect to have screening for many disorders without regard to race or ethnicity. Some screening panels provide genetic carrier testing for more than 100 different disorders. Many of the disorders are severe and affect a person’s quality of life from an early age. Some of the disorders are associated with early death.
What are the advantages of expanded carrier screening?
The main advantage is that it allows you and your partner to be screened for a much greater number of disorders than carrier screening based only on your ethnicity or race. People can be carriers for conditions even if they do not have a family history of the disorder or are not from the race/ethnicity noted to be at increased risk. The cost of expanded carrier screening may be about the same as screening for a single disorder.
What are the limitations of expanded carrier screening?
Because the panels test for so many disorders, it is common to test positive as a carrier for one or more disorders. Although most people who are carriers do not have any health problems, in rare cases it is possible you may learn that you are a carrier for a certain condition that can affect your future health. Some of the disorders included on the panel cause a disease in some people and not in others. It may not be possible to predict the severity of a disease or even if an individual will have the disorder.