Children born to older dads, teen mums and parents with a large gap in ages are at a higher risk of autism.
According to the largest multinational study to date linking autism and parental age, babies born to fathers who are between 35 and 44 and mothers in their 20s are most likely to suffer from the complex neurodevelopment disorder.
The children of teen mums were found to be 18 per cent more likely to have autism than those born to parents in their 20s, but the study of children born between 1985 to 2004 in Denmark, Norway, Israel, Sweden, and Western Australia showed that the risk increases with the age of the parents.
Of the 5,766,794 children involved in the study, 30,902 were diagnosed with autism spectrum disorder (ASD), with 10,128 eventually diagnosed with autism disorder.
Children with fathers aged 50 or over were found to be 66 per cent more likely to have autism compared to dads in their 20s. Mums who are over 40 have a 15 per cent higher risk of giving birth to a child with autism than their younger counterparts.
"After finding that paternal age, maternal age and parental age gaps all influence autism risk independently, we calculated which aspect was most important," study lead Dr. Sven Sandin PhD said. "It turned out to be parental age, though age gaps also contribute significantly."
Dr Sandin added: "Although parental age is a risk factor for autism, it is important to remember that, overall, the majority of children born to older or younger parents will develop normally."
