There are more than 7,000 rare diseases affecting over 30 million Americans according to the National Organization for Rare Disorders (NORD). Many rare conditions and disorders are caused by changes in our genetic information and some of these genetic changes silently run through healthy families. People who are pregnant or considering pregnancy may explore genetic carrier screening to identify these silent genetic changes so they can make informed family planning decisions. Carrier screening is routinely offered, but many people aren’t aware of it and have questions. If you are considering carrier screening or are just curious about your options, here are some things to know and consider.
Genetic conditions may be rare, but people who carry them are not.
Genes are packages of instructions that tell our bodies how to grow and function. Changes in our genes can make them work improperly and can result in medical problems or developmental differences. We get one copy of these genes from each our parents. If one out of the two gene copies is not working, you will typically have no symptoms and are called a “carrier.” Everyone carries these harmless genetic changes. In fact, most of us carry a few different genetic conditions. Autosomal recessive conditions, such as cystic fibrosis and sickle cell anemia, only happens if a child inherits a copy that doesn’t work properly from both genetic carrier parents.
A genetic condition will only occur if both genes inherited from parents do not work properly, shown on the right.
If everyone carries genetic conditions, should I be worried?
Finding out your genetic carrier status is more often reassuring and interesting, rather than concerning. While most carriers have nothing to worry about, there are a few exceptions.
- If you and your reproductive partner (spouse, significant other, sperm/egg donor, etc.) carry the same condition, there is a possibility that children will inherit the non-working copy from both parents and will be affected with the condition. Specifically, a carrier couple has a 1 in 4 chance (25%) in every pregnancy to have a child with the condition they carry.
- Rarely, carriers of specific genetic conditions may have an increased chance for specific health concerns. For example, Gaucher disease is a condition that affects the liver, spleen and bones when both copies of the GBA gene are not functioning. Individuals with one non-working copy of the GBA gene are carriers and do not develop liver, spleen or bone problems like those with Gaucher disease, but they do have an increased risk for Parkinson’s disease.
How do you know which condition you carry?
Genetic testing to find out which conditions you carry is available for any pregnant person or person considering pregnancy. We call this testing “carrier screening.” Carrier screening can be performed on a sample of blood or saliva and is ideally performed before you conceive. Some carrier screening panels only look for the most common conditions (sickle cell anemia, thalassemia, cystic fibrosis and spinal muscular atrophy) whereas more extensive carrier screening can test for hundreds of additional less-common conditions. While some conditions are more common in specific ethnic or ancestry groups, anyone can be a carrier of any genetic disease. Because of this, and because not everyone knows their full genetic background, many carrier screening panels are not focused on a particular ethnic group.
When should you get screened?
It is best to explore carrier testing options and undergo screening before you or your partner get pregnant. Carrier screening frequently involves testing both biological parents. It can be beneficial to get both parents tested at the same time, especially when larger carrier screening panels are ordered.
Screening before conception allows at risk couples to consider the full spectrum of reproductive options. Every person has unique values, needs and preferences and what you would do with testing information is a personal choice. Some families at risk for a genetic condition may want to know so they are more prepared and can test the baby immediately after birth. Other carriers want to take action to prevent the genetic condition and may consider technology such as in vitro fertilization (IVF). IVF involves taking sperm and eggs and creating embryos in a lab so that testing can be performed on embryos. This allows embryos without the condition to be selected for transfer.
What is the take home message?
Everyone carries genetic conditions and testing both parents prior to conception is ideal. Most people get reassuring results. Knowing ahead of time whether you are at risk allows for planning, potential prevention or earlier diagnosis of a genetic condition. Deciding whether to have carrier screening and what to do with the results is a personal decision. Genetic counselors are available to discuss the benefits and limitations of carrier screening and can help you navigate positive carrier screening results.
Find a genetic counselor in your local area or via telehealth here: findageneticcounselor.nsgc.org
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