Carrier Screening

What is carrier screening?

Carrier screening is a test that determines if you’re a carrier of certain genetic (inherited) health conditions. Being a carrier means you have a pathogenic variant (harmful change) in a gene that can cause a specific health condition. But carriers usually don’t have signs or symptoms themselves. Instead, carriers of a condition may have biological children with the condition if that child’s other parent is also a carrier.

Your carrier screening results remain private in your medical record and can’t be shared with people who don’t have access to your records without your consent. By law, health insurance companies and employers can’t discriminate against most healthy people who’ve had abnormal genetic testing.

What does it mean to be a carrier for health conditions?

Being a carrier means that there’s a chance that you can pass on a gene variant to your biological children. You’re born with two copies of each gene — one from each parent. Carriers of a condition have one copy of a gene variant. Your other, unaffected gene “overrides” the gene variant, so you usually don’t have signs of the health condition.

Most carrier screenings check for conditions that are autosomal recessive. These are health conditions that you can inherit if both your parents are carriers. Many people are carriers of autosomal recessive conditions but don’t know it. There often aren’t any known cases of the health condition in your family.

By contrast, you can be a carrier for an X-linked condition if you have two X chromosomes (like most people assigned female at birth). Again, most of these carriers have fewer — if any — symptoms than relatives who have an X chromosome with the variant on it and a Y chromosome. Some X-linked conditions, like fragile X syndrome, are often on carrier screening panels.

When is carrier screening performed?

Carrier screening is recommended for people considering establishing a pregnancy. If you choose to have carrier screening, ideally, it’s done before pregnancy. This way, you’ll know your future children’s risk of getting a genetic condition. Having carrier screening done at this stage gives you time to explore different ways to build a family, like:

• Adoption.
• IVF (in vitro fertilization) using donor eggs or sperm.
• Preimplantation genetic testing. This testing looks for genetic conditions in embryos created with a couple’s egg and sperm before implantation.

If not done before pregnancy, your provider should offer carrier screening during your first trimester of pregnancy. Carrier screening during pregnancy allows you to make healthcare plans that affect the remainder of your pregnancy. You can have additional tests — like amniocentesis or chorionic villus sampling (CVS) — to check for health problems in your baby. Your providers can also prepare for any special needs your baby may have soon after birth.

When would carrier screening be needed?

All couples should pursue carrier screening when thinking of starting a family. Collectively, it’s common to be a carrier. Most ethnic groups have a higher chance of being a carrier for at least one genetic disorder. People at a higher risk of being carriers are those who have someone in their family (previous child or relative) with an autosomal recessive or X-linked genetic disorder or who are known carriers of a genetic disorder.

Who performs carrier screening?

Providers that may perform your carrier screening test include:

• A fertility specialist.
• A genetic counselor or a medical geneticist.
• An OB/GYN.

What conditions does carrier screening test for?

Carrier screening checks for some of the more common autosomal recessive conditions, including:

• Cystic fibrosis.
• Fragile X syndrome.
• Sickle cell disease.
• Tay-Sachs disease.
• Thalassemia.

Expanded carrier testing

You can choose to have expanded carrier testing, which checks for more conditions than more limited carrier testing. Healthcare providers now recommend expanded carrier testing, which can include dozens of conditions in addition to the ones mentioned above, like:

• Congenital adrenal hyperplasia (CAH).
• Spinal muscular atrophy.
• Turner syndrome.
• Wilson disease.

Targeted carrier screening

If certain genetic conditions run in your family, you can have targeted carrier screening if you don’t want expanded carrier screening.

Some conditions affect people with certain ancestries more than others. If you’re one of them, your provider may recommend a carrier screening panel that looks only for those conditions.

How does carrier screening work?

Carrier testing requires a small amount of your blood, saliva or tissue from inside your mouth. Depending on your needs, your provider may perform a:

• Blood test.
• Saliva test.
• Tissue test, which involves rubbing a swab on the inside of your cheek.

How do I prepare for carrier screening?

If you’re having a saliva or tissue test, you may need to refrain from eating or drinking immediately before the test. Usually, there’s no other special prep needed for carrier screening.

What can I expect after carrier screening?

Your provider sends your blood, saliva or tissue sample to a specialized genetics lab for analysis. You may get your results back within a few days or weeks, depending on the type of test you had.

After you receive your results, your provider may recommend you talk with a genetic counselor. These experts are specially trained in genetic conditions and can:

• Answer your questions about being a carrier.
• Give you information to share with family members, if you choose to tell them your carrier status.
• Provide information about family planning options.
• Refer you to other healthcare providers if needed.

What are the risks of carrier screening?

You may feel a poke during a blood draw or have some minor soreness afterward.

Before having carrier screening, talk with your provider about the benefits and limitations of this test. This could include the small possibility of finding out that you have a mild form of the condition yourself instead of just being a carrier. Some people experience stress or anxiety over having carrier screening. Talk to your provider about your concerns and seek mental health support if you need it.

What do the results mean?

A negative result means the test didn’t detect any known genetic variants in your body. In this case, your children have a very low risk of inheriting certain genetic diseases. However, carrier screening can’t detect 100% of carriers for many conditions. A negative result doesn’t guarantee that your children will be free of all genetic health conditions.

A positive result on your carrier screening means you’re a carrier for one or more genetic health conditions. If your results are positive, consider whether your reproductive partner should also be screened.

If both you and your partner are carriers for the same autosomal recessive condition, each of your biological children has:

• A 25% chance (1 in 4) of inheriting two atypical genes and having the health condition.
• A 50% chance (1 in 2) of inheriting one atypical gene. This means they’re a carrier but won’t have the condition.
• A 25% chance of inheriting two typical genes. This means they aren’t a carrier and won’t have the condition.

When will I know the results of carrier screening?

Genetic testing usually takes several days to a few weeks to complete. Ask your provider when you can expect your results.

When should I call my provider?

Contact your provider if you:

• Haven’t received your results within the timeframe you discussed.
• Received your results but have questions about them.
• Want to discuss your options for building a family.

A note from Cleveland Clinic

Carrier screening can empower you to make important healthcare decisions and family planning choices. It may also provide peace of mind if you wish to have a biological child in the future. Discuss any concerns you may have with your provider and seek counseling for your mental health, if needed.