Genetic screening for autism
My partner’s brother has Aspergers Syndrome. My partner and I are interested in the link between Aspergers and genetics before we try for a baby ourselves. Is this something you can help with?
Dr Elfriede Ihsen
You are confronting an interesting issue, which requires careful consideration. Unfortunately OTARC can’t help you too much with your decision whether to try for a baby. We know, as you do, that Autism Spectrum Disorders (ASDs) run in families and must therefore be caused, at least in part, by some genetic abnormality. But even though there is a lot of research on which genes may be involved, we do not yet have a definitive answer.
There is wide agreement though that it is likely that a multitude of genes are affected, not just one, and that the genetic causes of ASDs are therefore complex. However, Fragile X is the only known genetic cause of Autism. Fragile X testing is available in Australia. You will need a referral from your GP to access this service, from a major hospital.
We also don’t yet have a test that could help us determine before birth whether a baby has an ASD. The earliest we can reliably diagnose ASD in children is about 18 months to 2 years. In the absence of clear physical indicators we look at behavioural symptoms for this diagnosis.
But even though we don’t know enough yet about the genetics of ASD, we do know that about 1% of children in the Australia population and elsewhere have an ASD. This means that the chances of any family having a baby with an ASD are 1 in 100, even if there were nobody else in the family affected by the disorder. ASDs are approximately four to five times more common amongst boys than amongst girls, with boys having a 1 in 50, and girls a 1 in 250 chance of developing an ASD.
Unfortunately, there are no statistics that help you in your particular case. As far as we know, nobody has done any research to determine whether the chances of having a child with an ASD increases if there is a member in the extended family affected with the disorder, as is the case in your family. We do know however, that the risk of having a baby with an ASD increases to 1 in 5 (20%) if this baby has an older sibling with the condition. If this baby were a boy, he would have a 26% chance (1 in 4), for a girl the chance would be 9% (1 in 11). This risk increases further if there are more than one older siblings or when there is an affected identical twin.
You could discuss this issue with a genetic counsellor who may help you identify some ways of decreasing risk, such as ‘sorting’ female and male embryos (as the risk of ASD is lower for females). But be aware that we do not necessarily recommend this intervention for ethical reasons.
Please also consider that not all children and adults with an ASD are severely affected and there is no way of predicting how mildly or severely affected a child may be, even if this child already has a sibling with severe symptoms. Also consider that many people with an ASD have contributed significantly to our society and are happy and successful children and adults.
Interview with Professor David Amaral on PBS News Hour
Explores the different possible genes involved in autism.
Article on The Conversation “Mothers’ genes may be why autism is more common in boys”