Family Considerations

If you have a child with spinal muscular atrophy (SMA) or are a carrier of the SMA gene, you face some serious decisions. It can be helpful to learn more about the condition and consider the risks and choices involved in coping with SMA in your family.^1,2

Risks for families

SMA almost always runs in families. The culprit is a damaged survival motor neuron 1 (SMN1) gene. SMN1 is recessive, which means you can be a carrier of the disease but not have any symptoms. If you inherit two damaged SMN1 genes, one from each parent, you are more likely to have SMA.^1,2

These statistics explain it best:^1-4

• Two carrier parents have a 1 in 4 chance of having a child with SMA, a 1 in 2 chance of having a child who is a carrier, and a 1 in 4 chance of having a healthy child.
• A carrier parent and a healthy parent have a 1 in 4 chance of having a carrier child.
• A parent with SMA and a healthy parent will have a carrier child.
• A parent with SMA and a carrier parent have a 1 in 2 chance of having a child with SMA and a 1 in 2 chance of having a carrier child.
• Two parents with SMA will have a child with SMA.

Families often have more than one child with SMA, and siblings with SMA often share the same SMA type.^1-4

Discussions for families

SMA can be an emotional topic that is difficult to talk about. But having detailed conversation about SMA between parents as well as with children is critical. Gear discussions with children to their age and mental maturity. Make sure to be sensitive to everyone’s feelings.⁵

Talking to siblings of children with SMA

Very young children may notice that their sibling with SMA has fewer abilities than them. You can explain that movement, eating, and breathing difficulties are part of the disease.⁵

A child with SMA needs ongoing attention. Reassure their siblings of their importance in the family, and keep them involved. For example, you can ask them to help with the caregiving.⁵

Explaining what causes SMA

As your children age, you can explain how SMA is passed down in families. Older children may be able to understand what genes are. These are like instructions that tell their bodies how to grow and develop.^4,5

Genes come in pairs, one from each parent. If a gene is not normal, it cannot do its job. Important events in the body do not happen correctly. In people with SMA, this includes muscle growth and related functions.^4,5

Children under age 15 or so may not understand what SMA in the family means for them. So, make sure to answer questions as they arise, but plan for in-depth discussions after that age. You can then discuss the risks of being a carrier, family planning, sibling screening, and genetic testing.^4,5

Choices for families

As your family discusses SMA and its effects, you may consult a genetic counselor about your genes. This expert can help you find out whether you are a carrier of SMA. A simple blood test detects about 90 percent of carriers.^4,6

If you are a carrier, you will want to think about the possible outcomes of having children. You may want to know this if you:^3,4,6

• Are planning to have your first child
• Are already pregnant
• Already have a child with SMA and want more children
• Are a sibling of someone with SMA

Testing for SMA risk

You may decide to limit your family size to avoid having a child with SMA. You may also have further testing done so you can make a more informed decision.^3,4,6

For example, if you are pregnant or planning to get pregnant, you have several options. A specialist can test your blood together with a DNA sample of a family member with SMA. Or a doctor can test your newborn.^3,6

Doctors may also test the fetus prior to birth with more invasive tests such as chorionic villus sampling (CVS) or amniocentesis. They can do CVS at 11 weeks of pregnancy by sampling the placenta. Or they can conduct amniocentesis at 15 weeks by sampling the amniotic fluid.^3,6

Both tests carry a 1 in 200 risk of causing a miscarriage. Before testing, you and your partner will need to discuss what to do if the result is positive.^3,6

Options other than traditional pregnancy and birth

If you want to have more children without the risk of passing SMA, in vitro fertilization with preimplantation genetic testing (IVF with PGT-M) may be an option. This procedure uses your and your partner’s eggs and sperm to create embryos in the laboratory. The embryos are tested for SMA, and a non-SMA embryo is then transplanted into the mother’s womb.⁶

You can also have IVF with a non-carrier donor sperm or egg. Or you may choose to adopt a child who has had genetic testing for SMA.⁶

Having SMA in your family means you may take a different road than other families. But careful consideration of the risks and realities will help you make wise decisions. You can equip your family to thrive together now and in the long run.^1-6