What carrier screening is.
Carrier screening looks at your genes, not the pregnancy. It helps you understand whether you or your partner could pass certain inherited conditions on to a child.
What it looks at
Genes are pieces of DNA that help tell our bodies how to grow and work. We all have small differences in our genes. Most do not cause any problems.
Sometimes, a difference in a gene can cause an inherited condition if it is passed on in a particular way. Carrier screening looks for these specific differences.
For example, screening commonly includes:
Cystic fibrosis, which mainly affects the lungs and digestive system.
Spinal muscular atrophy, which affects the nerves that control muscles and can cause serious muscle weakness.
Fragile X syndrome, which can affect learning, development and behaviour.
Different carrier screens look at different numbers of conditions. Expanded screening looks across many more genes than the standard three-condition screen.
What being a carrier means
For many of the conditions we screen for, you have two copies of the relevant gene: one inherited from each biological parent.
If one copy has a change linked to a condition but the other copy works normally, you are called a carrier.
Being a carrier usually does not mean you have the condition yourself. In fact, most people have no symptoms and no family history, so they would have no reason to know without testing¹.
What becomes important is whether your partner carries a change in the same gene.
If you both carry the same recessive condition, each pregnancy has²:
1 in 4 chance the child has the condition
1 in 2 chance the child is a carrier
1 in 4 chance the child neither has the condition nor is a carrier
It matters when both partners carry a change in the same gene, because a child can inherit a changed copy from each of you. Fragile X syndrome works differently. It passes down from the mother, so her result matters on its own.
How common carrying is
Being a carrier is not unusual.
Most carriers are healthy and have no known family history of the condition they carry. A gene change can quietly pass through a family for generations without anyone knowing it is there².
And the more genes you look at, the more likely it is that you will find something. That does not mean something is wrong with you. It is part of normal human genetic variation.
Carrier screening is really about whether your results and your partner’s results create an increased chance for a future child.
Who should consider it
Carrier screening can be considered by anyone planning a pregnancy or in early pregnancy³.
You do not need a family history of a genetic condition to consider testing.
If a condition does run in your family, tell your doctor, as you may need more specific testing.
When to do it
You can screen before or during pregnancy.
Before pregnancy is often the most useful time because it gives you more time to understand your results, test your partner if needed, and plan ahead.
What a result tells you
A carrier result does not mean your child will have a condition.
For many conditions, your partner’s result helps show whether there is an increased chance for a future child.
A clear result also does not rule out every genetic condition.
A clearer place to start.
Carrier screening helps you know where you stand and plan for your family with peace of mind.