If you have been planning on starting a family with your partner or have begun your journey of starting a family using a fertility center, you might have heard about a test called carrier screening.
Some important genetic concepts
Genes are recipes or instructions to make sure our bodies work well. We all have the same >20,000 genes and we all have two copies of these 2 genes; one that we receive from our biological mother and the other one from our biological father.
A genetic condition is caused when a specific gene is not working properly. There are different ways these conditions can be inherited, including a dominant or a recessive inheritance pattern. A recessive genetic condition requires both parents to be carriers for the same genetic state, while a dominant one only requires one parent.
Carrier screening is genetic testing for recessive conditions
In carrier screening, most genetic conditions that are tested have a recessive inheritance pattern where both biological parents must be carriers for the same situation for their child to have a risk to be affected with the condition.
The conditions that are screened through carrier screening are generally severe genetic conditions for which an affected child would show signs and symptoms from birth or early infancy. These severe conditions are generally not detectable through other tests during pregnancy, such as ultrasound.
Anyone can be a carrier
Being a carrier of a serious genetic condition does not usually affect one’s personal medical health: a carrier generally does not have that affectation and will not develop it.
Anyone can be a carrier without knowing it. They could be completely healthy, their whole family is healthy, everyone in their family has had healthy children and they could still be a carrier of a serious genetic condition.
Being a carrier mainly affects one’s reproductive health. If a carrier of a serious genetic condition has a reproductive partner that is also a carrier of the same condition, together they will have a 25% chance of having a child with that condition (and a 75% chance of having a child that will not have that condition). Reproductive partners that are both carriers for the same genetic condition will not necessarily have a baby affected with the condition!
If one reproductive partner tests negative, the chance of having a child affected with the genetic condition is usually reduced, and there is a low chance of this specific condition in a future pregnancy.
Expanded carrier screening
The number of recessive genetic conditions that can be tested through carrier screening has exponentially grown in just the past 10 years, leading to the term “expanded carrier screening”. Expanded carrier screening (sometimes referred to as comprehensive carrier screening) is carrier screening for a large number of genetic conditions that goes beyond one’s ethnicity and family history.
Current expanded carrier screening tests can screen for over 200 conditions. The main genes related to hereditary cancer, hereditary dementia, hereditary cardiovascular conditions, as well as many other adult-onset conditions, are not included in expanded carrier screening.
Important to note
Although expanded carrier screening can test for many genetic conditions, it cannot test for everything. A negative result reduces one’s risk of having a child with a recessive genetic condition, but it is important to remember that the risk is still not zero. All recommended screening during a future pregnancy should still be considered.
Expanded carrier screening is voluntary. Your genetic testing results are confidential and protected by the Genetic Non-Discrimination Act in Canada. This act protects Canadians from having to share a genetic testing result or undergo a genetic test to obtain a service or enter into a contract. This applies to insurance companies, who cannot use the results of a genetic test to determine coverage or premiums.
If you are interested in learning more about expanded carrier screening or accessing this type of test, speak with your health care provider or contact us to make an appointment with one of our genetic counsellors.