If you’re an expectant parent, or planning a pregnancy, you probably want to know all you can about your future family. Genetic carrier screening allows for a closer look at your genes, to see if there is a chance your baby could inherit certain genetic disorders. It’s a simple test that can help you plan with confidence.
What is spinal muscular atrophy?
Spinal muscular atrophy (SMA) is the most common inherited cause of infant death.
It affects a person’s ability to control their muscles, including those involved in breathing, eating, crawling and walking. SMA has different levels of severity, none of which affect intelligence. However, the most common form of the disorder causes death by age two. About one in every 6,000 to one in every 10,000 babies born in the US has SMA.
Watch a video to learn more about genetic carrier screening for hereditary disorders.
How is SMA inherited?
You have two copies of every gene; one copy was inherited from your mother and one copy from your father.
A person who has one normal gene and one abnormal gene that can cause a genetic disorder, is called a carrier. A carrier is not affected with the disorder, but they can pass on the abnormal gene to future generations.
If both parents are carriers of SMA, then their children are at risk of being affected by the disorder. A child who inherits one copy of the abnormal gene from each parent (resulting in two copies), will be affected by SMA. With each pregnancy, there is a 1 in 4, or 25%, chance of this happening.
Who can be a carrier?
Anyone can be a carrier of a genetic disorder, even if there is no family history. Many times, genetic disorders stay “hidden” in a family. You could be a carrier and not know it until a child is born with the disease.
About 1 in 40 people in the US are carriers of SMA. It occurs in people of all ethnicities, but is more prevalent in some groups.
If someone in your family has SMA, your risk of being a carrier is greater.
How is the test performed?
A simple test of your blood or saliva can determine with a high degree of accuracy whether you are a carrier of SMA.
What does a negative result mean?
A negative result indicates you are not a carrier of SMA, which can provide significant peace of mind. However, no test can detect 100% of genetic carriers. Even if your test results are negative, it is still possible that your baby could inherit the genetic disorder, but the chance is extremely small.
What does a positive result mean?
A positive result tells you that you are a carrier of SMA, and you could be at risk of having an affected child. If you are a carrier, it is important to find out if your partner is also a carrier.
If you and your partner are both carriers, then you are at risk of conceiving a child who is affected with the disorder. With each pregnancy, there is a 1 in 4, or 25%, chance that your baby could be affected.
What if my partner and I are at risk for having a child with SMA?
If you are pregnant, prenatal diagnostic tests can tell you whether your baby is affected by the disorder.
There are also options to prevent genetic disorders prior to pregnancy. These include in vitro fertilization, using a diagnostic test to select healthy embryos for implantation, or using donor eggs or sperm from a person who is not a carrier. Some couples choose to adopt a child. Your healthcare provider or a genetic counselor can discuss these options in greater detail.
Is genetic carrier screening required?
All testing is optional. The decision to accept or decline genetic carrier screening is completely up to you.
Talk to your healthcare provider to find out if this test is right for you.