More and more woman these days are waiting to have children. There were always documented risks to waiting until after 40, both for mother and child. But now there's another one -- as a woman gets older, the chances of her having a baby with autism increases.
A new study published in the journal Autism Research says the risk of having a child with autism increases by 18 percent for every five years a woman ages before giving birth. That means a 40-year-old woman is 50 percent more likely to have a child with autism than a mother who is age 25 to 29.
The father's age only comes into play when the mother is under 30, and he is older. For example, children of mothers under aged 25 and fathers over 40 are twice as likely to have autism as compared to children with young mothers and fathers.
"This study challenges a current theory in autism epidemiology that identifies the father's age as a key factor in increasing the risk of having a child with autism," said Janie Shelton, the study's lead author and a doctoral student at the University of California, Davis. "It shows that while maternal age consistently increases the risk of autism, the father's age only contributes an increased risk when the father is older and the mother is under 30-years-old. Among mothers over 30, increases in the father's age do not appear to further increase the risk of autism."
Researchers focused on birth records of nearly 5-million children in California between 1990-1999. Of those, there were 12,000 cases of autism.
Just as the cause of autism itself is unknown, this new study says it is unclear why older mothers are at a higher risk of having children with autism. Nonetheless, parental age is likely just one factor, researchers say. While autism diagnoses increased 600 percent among Californians in the 1990s, parental age likely only contributed to about 5% of that increase.
photo credit: fortheloveoffiona