Spinal Muscular Atrophy

Spinal Muscular Atrophy Carrier Screening & NIPT

With multiple emerging spinal muscular atrophy (SMA) treatments that are initiated at birth, early knowledge can be critical. The first step of UNITY Screen™ is to understand if you are a carrier for SMA. For carriers who are pregnant, non-invasive prenatal testing is automatically performed to determine if the pregnancy may be at high-risk for the condition.

Carrier Rate/Incidence

1 in 54 people are carriers of spinal muscular atrophy and 1 in 10,000 babies are born in the U.S. with spinal muscular atrophy

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Common Symptoms

Progressive muscle weakness in the motor neuron cells of the spinal cord affecting muscles that control breathing, eating, and movement

Emerging Treatments

Several FDA-approved treatments are available and should be initiated as soon as possible after diagnosis for the best outcomes

What is UNITY Fetal Risk Screen(™) for spinal muscular atrophy?

UNITY Screen (™) starts with carrier screening for spinal muscular atrophy to identify carriers who may have an increased risk of having a baby with SMA. If you are a carrier, UNITY Screen (™) automatically performs single-gene NIPT on your sample to determine your baby’s risk of having spinal muscular atrophy. While not diagnostic, UNITY Screen (™) offers early identification of pregnancies at high-risk for SMA, which is crucial for informed family planning and early intervention.

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The American College of Obstetricians and Gynecologists recommends that anyone planning to start a family or those who are already pregnant be offered carrier screening for inherited conditions, including spinal muscular atrophy.

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What is spinal muscular atrophy?

Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder that causes the loss of function of motor neurons in the spinal cord and brainstem, leading to muscle weakness and atrophy. SMA is caused by mutations in the SMN1 (Survival Motor Neuron 1) gene, which is responsible for producing the SMN protein essential for the survival of motor neurons. When the SMN1 gene is not functioning properly the body doesn’t produce enough of this protein causing motor neurons to degenerate and muscles to weaken over time.

Common symptoms of SMA include progressive muscle weakness and wasting, decreased muscle tone, limited mobility, and difficulties with swallowing and breathing. The severity of symptoms can vary widely depending on the type of SMA, which ranges from Type 0 (most severe) to Type 4 (least severe). Early onset SMA (Types 0 and 1) usually presents severe symptoms in infancy, while later onset SMA (Types 2, 3, and 4) presents milder symptoms that appear in childhood or adulthood.

Emerging gene-therapy treatments for SMA have shown promising results when started soon after a diagnosis of SMA. These treatments have been effective in improving motor function, slowing disease progression, and enhancing the quality of life for individuals with SMA. Early diagnosis and intervention are crucial for the best outcomes, making carrier screening, prenatal diagnosis, and newborn screening important tools in managing SMA.

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How is spinal muscular atrophy inherited?

Spinal muscular atrophy is an autosomal recessive condition. This means that a person must inherit two non-functional SMN1 genes, one from each of their parents, to be affected with SMA. Parents who carry one functional gene and one non-functional gene are known as carriers and typically show no symptoms.

If both parents are carriers of SMA, there is 25% chance with each pregnancy that their child will inherit two non-functional genes and develop SMA, a 50% chance that their child will inherit one non-functional gene and be a carrier like their parents, and a 25% chance that their child will inherit two functional genes and not be affected or a carrier.

Chart showing Alpha-Thalassemia inheritance from two unaffected carriers. Both parents with working genes has a child with no condition and is not a carrier. One parent with non-working gene produces child with no condition but is a carrier. Both parents with non-working gene has condition. 75% of children do not have the condition.

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Who should consider spinal muscular atrophy screening?

Carrier screening for spinal muscular atrophy is recommended for anyone who is planning a pregnancy, currently pregnant, or has a family history of SMA. UNITY Screen (™) is a simple blood test to determine your carrier status and the risk of having a baby with spinal muscular atrophy. If your results show a high risk of any of the conditions screened, you can discuss additional testing either before or after your delivery with your healthcare provider or one of our genetic counselors.

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UNITY Screen (™) Carrier Screening & sgNIPT workflow

With UNITY Screen™, carrier screening is performed first to see if you’re a spinal muscular atrophy. If you're not a carrier for SMA, the chance your baby is affected is extremely low. If you are found to be a carrier, the second step is to assess your baby's risk for SMA. All it takes is a blood sample after 10 weeks in pregnancy.

Consult
The UNITY Screen™ NIPT is ordered through your healthcare provider. You can schedule a complimentary genetic counseling session to answer any questions about the test before or after your blood is drawn.

Test: As early as week 9
Your blood sample can be collected in the doctor’s office, at a local lab, or through our mobile services. Your blood sample is shipped to our CAP/CLIA certified laboratory in northern California.

aneuploidy NIPT + fetal antigen results: As early as week 10
Within about one week from lab receipt, your doctor will receive the baby’s risk score for aneuploidies (chromosome conditions) and fetal antigens (if added). You will receive a text or email indicating your results are available on our portal, or your healthcare provider may call you with the results.

carrier status + single-gene NIPT results: As early as week 11
Within about two weeks from lab receipt, your doctor will receive the results of your maternal carrier status testing and single-gene NIPT. If you were found to be a carrier for any of the recessive conditions, single-gene NIPT is automatically run to determine your baby’s risk of being affected. You will receive a text or email indicating your results are available on our portal, or your healthcare provider may call you with the results.

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What do spinal muscular atrophy screening results mean?

Your UNITY Screen (™) results will tell you if you are a carrier for spinal muscular atrophy, or other recessive conditions. Then, if you are a carrier and currently pregnant for one or more of the conditions screened, single-gene NIPT will automatically be performed on your sample. Your report for UNITY Screen (™) will show what your baby’s risk of having spinal muscular atrophy is. Results are usually reported as “low-risk” or “high-risk” and your report will have specific information about your sample.

UNITY Screen (™) results are not diagnostic, so there is always the option for additional confirmatory testing to be performed to understand more about any high-risk results. There are options both before and after delivery.

Before Birth: Testing during pregnancy can be performed by obtaining a sample of placenta (chorionic villus sampling or CVS) or fluid around your baby (amniocentesis) which both contain DNA that is representative of your baby. A CVS is ideally performed between 10 to 13 weeks in pregnancy while an amniocentesis is typically performed between 15 to 24 weeks in pregnancy. Both procedures are generally safe, but have a small risk for pregnancy complications, including miscarriage.
‍After Birth: Testing for your baby can be performed after birth through a blood test. In addition, all babies born in a hospital in the United States are automatically screened for spinal muscular atrophy. The majority of babies with spinal muscular atrophy will be diagnosed through this screening process. However, in rare cases, a diagnosis may be missed or incorrectly diagnosed.

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Frequently Asked Questions

Is there a cure for spinal muscular atrophy?

Currently, there is no cure for spinal muscular atrophy (SMA), but significant advancements have been made in treatments that improve symptoms and quality of life. Ongoing research includes gene therapy, new medications, and clinical trials. Research efforts are ongoing, providing hope for more effective treatments and potentially a cure in the future.

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What are the different types of SMA and how do they differ?

Historically, before many of the disease modifying treatments were available, SMA was categorized into five separate types (Type 0,1,2,3 and 4). These types were distinguished by age of onset and the highest physical milestone a person achieved (ex: crawling, walking unassisted, walking with mobility device). However, this system doesn’t capture the newest generation of infants and children with SMA treated early in life. With newborn screening programs and more treatment options more infants are being diagnosed and receive treatment prior to the onset of symptoms, blurring the lines between distinctive SMA types.

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What are the treatment options for spinal muscular atrophy?

Treatment for spinal muscular atrophy (SMA) focuses on managing symptoms and improving quality of life. Individuals with SMA typically benefit from multi-disciplinary supportive care including: physical therapy, respiratory support, nutritional support, and orthopedic interventions to manage symptoms and complications. Additionally, there are many therapies designed to treat SMA in different ways including gene therapy, antisense oligonucleotides, and oral medications that all work to increase the functioning SMN protein in the body.

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