What is genetic carrier screening?

How does carrier screening work?

Carrier screening involves taking a sample of your blood or saliva. The samples are tested for changes or differences (variants) in your genes that can cause certain genetic conditions.

If your results are positive, this means you carry the gene variant that’s linked to a certain genetic condition. This condition could be passed to your child.

A positive result does not guarantee your child will inherit a condition but indicates a higher chance that they could.

What does carrier screening test for?

Many tests look for conditions where a baby is more likely to be affected if both biological parents carry the same changed gene. Some tests also include conditions that are passed on through the X chromosome.

The conditions included depends on the test (sometimes called a ‘panel’). Common examples include:

• cystic fibrosis (CF)
• spinal muscular atrophy (SMA)
• sickle cell disease
• fragile X syndrome

‘Expanded’ carrier screening is another option. It checks for a larger number of conditions, most of which are rare.

You can also have ‘targeted’ carrier screening. This means the test is chosen because of:

• your family history of genetic conditions
• your ethnicity

Genetic carriers are usually asymptomatic. This means they don’t show any symptoms of the conditions themselves. Anyone could be a carrier of a genetic variant without knowing, which is why the screening test can be helpful.

Who can have carrier screening?

You may wish to have carrier screening if you’re planning a pregnancy. You can also have it if you’re already pregnant, although it’s recommended to take the test within the first 12 weeks of pregnancy. The test can help you better prepare for your pregnancy and make informed decisions.

Both biological parents can have the test. Usually the person carrying the child will take the test first. If they are a carrier, then the second parent can take the test. The chance of a child being affected by a condition is higher if both parents are genetic carriers of the same condition.

You can also have carrier screening if you’re an individual planning a pregnancy using an egg or sperm donor.

If you’re planning to have children and would like to have carrier screening, speak with your healthcare provider about the options.

What should I do if I’m a carrier?

Being a genetic carrier is not uncommon and does not mean your child will inherit a genetic condition. The screening test isn’t designed to scare you, but it can give you more information about the chances of your child inheriting certain conditions.

You can discuss a positive result with your healthcare provider. They’ll be able to explain what the results mean and how it could affect your child.

What you do with the information from the test is completely your choice. There are options to have more tests during pregnancy to check whether your child has inherited the genetic condition. Or you might wish to consider other methods of pregnancy, such as IVF.

Your doctor can give you more information about the options to figure out what’s best for you. It can also be helpful to speak to loved ones for support if you need it.