All people are carriers for different genetic conditions. A carrier is someone who has a genetic mutation (abnormal variation) in one of their two copies of a particular gene, which are located on our chromosomes. A carrier of a genetic condition typically does not have any signs or symptoms of a disease because they have one working copy of their two genes.
When both parents are carriers for the same genetic syndrome, each parent can pass on their mutated (non-working) gene to the child. This means that the child has no working copies of that specific gene, which causes symptoms of a genetic syndrome. There is concern for the pregnancy when both the mother and her partner are carriers of a particular genetic syndrome, because the chances of the child inheriting the syndrome are much higher.
Carrier screening can help an individual or couple determine if they are carriers of a recessive genetic disease such as cystic fibrosis. (About 1 in 25 people are a carrier for cystic fibrosis.) The results provide information about your reproductive risk and whether you might have a higher chance of having a child with a genetic condition. If your reproductive risk is higher, you may require additional care during pregnancy.
What are the chances of a carrier couple having a child with a genetic syndrome?
If both a woman and her partner are carriers for the same recessive condition, each child has a 1 in 4 (25%) chance of having the condition.
Some less common genetic syndromes, which have more complex patterns of inheritance, may have a higher or lower risk than 1 in 4. Your genetic counselor will review this information in detail if you are a carrier for one of these syndromes.
Some couples have a higher chance of being carriers for the same condition, including those of certain ethnic backgrounds, those who share a common ancestor or those who have a family history of a genetic condition.
What does a carrier screen look for?
Carrier screening can help genetic counselors determine if there is a higher chance that a child will be born with certain recessive genetic syndromes like the following (and many others):
How is carrier screening performed?
We can perform carrier screening before or during pregnancy. Some parents may decide to have carrier screening as part of their family planning. (For example, if they have a personal or family history of genetic defect or condition, such as a heart defect.) Others may opt to receive carrier screening during pregnancy.
To perform a carrier screening, our genetic counselors will collect a blood sample from either mom or dad, or both.
When can I receive carrier screening?
Carrier screening is available before or during pregnancy to help determine if a couple has a higher risk of having a child with certain genetic conditions.
How long will results from a carrier screen take?
Results from a carrier screen are usually available 14 to 21 days after your visit and blood draw.
What are the risks of a carrier screen?
Because carrier screening is non-invasive and performed after a normal blood draw, the risk is very low.
How are carrier screening results interpreted?
Carrier screening can determine if a mother (or a couple) has an increased risk of their children inheriting some genetic conditions.
- A negative (normal) carrier screening result means that a mother’s (or couple’s) risk of having a child born with certain genetic conditions is greatly reduced. However, it does not eliminate the risk.
- A positive (abnormal) carrier screening result indicates that there is increased chance for the child to inherit a genetic condition. If your result is positive, we often recommend additional testing for your partner to determine if they are also a carrier of the same genetic syndrome. This provides the most accurate estimate of your risk of having a child with a genetic syndrome.
Carrier screening does not provide information about risk for chromosome conditions, such as Down syndrome, or adult-onset conditions, such as Alzheimer’s disease. If you are concerned about your risk for a chromosome condition in your pregnancy, you may consider cell-free DNA screening or maternal serum screening in addition to carrier screening.
What if my carrier screening results are abnormal?
If results show your children are at an increased risk, a genetic counselor can help you understand your results and discuss your reproductive options. These options may include assisted reproductive technologies, prenatal diagnosis through chorionic villus sampling (CVS) or amniocentesis, or guidance in preparing for the birth of a child with a genetic condition.