All of us are now very much aware of exorbitant cost involved in treating children with SMA. However, there are many ways we can prevent a child being born with SMA. Therefore, it is very important to make sure that those at risk of having baby with SMA understand such preventive measures.
Author
Dr. Saudabi Valappil
Dr Saudabi is a Consultant in Obstetrics and Fetomaternal Medicine, currently working in Corniche Hospital, Abu Dhabi. She graduated from Calicut Medical College in Kerala, South India in 1995. AIer completing her Master’s degree in Obstetrics and Gynecology in Calicut Medical College , Dr Saudabi moved to the UK where she completed higher training in Obstetrics & Fetal Medicine . She worked as consultant in South Manchester, UK before moving to UAE in 2015.
What is SMA?
Spinal muscular atrophy or SMA is a genetic condition that causes muscle weakness and serious problems with muscular functions such as movement, breathing, swallowing etc. It is a rare but serious condition affecting about 1 in 8000 children. There is no cure for this condition; however, treatment options such as gene therapy are available which is highly expensive and not affordable for most patients. Hence it is important to consider the options of preventing birth of a child with this inherited condition.
How is SMA inherited?
It is important to know how the disease is inherited to learn about the tests and options available for you.
SMA is a genetic condition and most cases are inherited in autosomal recessive pattern, which means two copies of the faulty SMA genes are transmitted – one from each parent to cause the disease. This leads to reduced production of SMN protein leading to weakness of the muscles which worsens as the child is growing. If one copy of faulty SMA gene is present in any person, they are called carrier of SMA disease. In reality they are normal but they transmit this faulty gene to their children by chance.
Being an autosomal recessive condition:
A person will have SMA if they inherit two faulty copies of the SMN1 gene, one from each parent.
A person who carries one faulty copy of the gene and one healthy copy will not have the condition but he or she will be a carrier. They will not have any symptoms, but the faulty gene can be passed on to their children.
So, parents who are carriers are asymptomatic.
If both parents are carriers, there is:
1 in 4 chance (25%) that the child will have the disease.
1 in 2 chance (50%) that the child will be a carrier with one faulty gene but without any symptoms.
1 in 4 chance (25%) that the child will be completely normal.
So overall there is only one in 4 chance that the child will be diseased and 3 out of 4 chance that the child will have a normal life.
What should I do if I am planning to get pregnant?
If you have a child with SMA or if any of your family members are affected with SMA, a genetic blood test can be done to determine whether you are a carrier for SMA or not.
If you know that you are a carrier, do the test on your husband to check whether he is also a carrier.
If only one parent is a carrier, the children will not be affected; however, they can be a carrier.
If you and your husband are carriers and you are planning to have a baby, you have the following options. However, it is important to find out the nearest hospital where these facilities are available.
Pre-implantation genetic diagnosis (PGD) with IVF treatment – where your eggs are fertilized with your husband’s sperm in a laboratory and the resulting embryos are tested for SMA before it is put in the womb. In that way, you can make sure that your baby will not have SMA for 100%.
If PGD is not available, the next option is:
To do IVF treatment (In vitro fertilization) with donated sperm or eggs from the donor without faulty SMA gene to get pregnant. If you are going for this option, you need to understand that the biological father or mother will be different depending on whether you receive sperm or egg from others.
If the above options are not available, or not acceptable for you or you became pregnant before you made a plan, there are tests available to do in the early part of the pregnancy so that you can decide whether you want to continue pregnancy or not. These tests can be done to check if the baby is affected.
These are
Chorion villus sampling (CVS): A sample of cells from the placenta is collected through a needle passed through the uterus and tested for faulty gene. This is performed from 11-14 weeks of pregnancy.
Amniocentesis: A sample from the amniotic fluid (the fluid surrounding the baby) is tested for the faulty gene. This is done from 15 weeks onwards.
Both tests are associated with about 1% risk of miscarriage.
If the test results show that your child has two faulty SMA genes, your baby will be born with SMA.
In this situation, you have two choices:
You can decide to end the pregnancy. In many countries, the law allows terminating pregnancy in this situation.
Some women decide to continue the pregnancy and explore treatment options.
It is important that you understand the possible outcome for your child before you take this important decision.
Knowing about your child’s condition at an early stage of pregnancy may help you to make an informed decision about the pregnancy and be prepared at birth.
If you are planning to continue your pregnancy, you should find out your nearest center where your newborn baby with SMA can be supported initially and treated.
