Making sense of autism risks

After my son was born with a random genetic change that my husband and I don't carry, I was told by geneticists that if I was to get pregnant again, the chance of having a second child with this condition was less than 1 per cent.

The genetics counsellor described those odds this way: "You have EVERY chance of having a perfect baby next time!"

I was given the green light for more kids.

So I was surprised to read a story about a Swedish study in the New York Times Motherlode column yesterday that suggests pregnant women shouldn't take antidepressants because they may increase the risk of autism without intellectual disability in a child by .6 per cent.

The baseline risk for having a child with autism is about 1.1 per cent (1 in 88 children), so this would bring the overall risk to under 2 per cent.

In other words, using antidepressants while pregnant may increase the risk of having a child with autism without intellectual disability by less than 1 per cent—the same odds I was given of having a second child with a rare, spontaneous genetic change.

The same risk deemed by my geneticists to be so small that it shouldn't be a factor in my decision to have more children.

While I had a greater than 99 per cent chance of having a second healthy baby without my son's genetic condition, this Swedish study suggests women using antidepressants have a greater than 98 per cent chance of having a healthy baby without autism.

The hitch in the study was that a causal link wasn't found between antidepressant use and the .6 per cent increase in risk of having a child with autism. The researchers said the tiny increase in risk could be caused by the antidepressants—or it could be caused by the depression itself.

Kind of a big question mark as to what the study means!

Yet the headline on the Motherlode piece reads Study Links Autism with Antidepressant Use During Pregnancy and the story doesn't mention the size of the possible increase in risk (.6 per cent).

Many readers commenting on the article imply that antidepressants have been found to be a major risk factor for autism.

They haven't!

According to the March of Dimes, a woman has a 3 per cent chance of having a child with a birth defect.

This means that the risk of having a child with any birth defect when the mom doesn't use antidepressants is higher than the increased risk for autism suggested by antidepressant use in this study.

The Swedish study "is very important in highlighting which biological pathways may be involved in how autism develops, but the information isn't translatable to counselling an individual woman who wants to have a baby because the additional risk is too small," says Evdokia Anagnostou, a child neurologist who leads a clinical research program in autism at Holland Bloorview.

"The study is helpful in explaining the increase in autism rates in a huge population, but it doesn't identify antidepressant use as a major risk factor in individual cases," Evdokia says.

She likens it to a study last year that found that men in their 40s are more likely than those in their 20s to have a child with autism, but the overall risk was still low, at 2 per cent. Does this mean mean older men should stop having children?

“If someone asks me ‘Do you think I should not have a baby because I’m 40?’ I would say you absolutely should have a baby. The majority of babies born to 40-year-olds are perfectly healthy.”

Evdokia emphasized that autism is “a multi-factorial disease that can’t be prevented at this point. Paternal age can now be seen as one of many contributors to risk"—but father's age and antidepressant use in moms don't explain the majority of risk.

“There are many, many reasons why you may end up with a child with autism and in these cases the child gets this extra little hit. But most of the time a child needs to have many hits to get autism.”

Other factors that increase risk include a parent's genetic makeup, such as having a sibling with autism or family members with autoimmune or mood disorders; the fetal environment, including infections during pregnancy and exposure to fertility and other drugs; and possibly some environmental toxins.

When considering treatment of pregnant women with depression, it's important to remember that untreated depression can have negative impacts on children. In this 2013 study, children of depressed moms who weren't treated had behavioural problems in early childhood, while those whose moms took antidepressants didn't.