Here’s why fever in pregnancy is tied to a 40 per cent increased risk of autism for babies

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Research author Dr. Mady Hornig shares her findings on the impact of prenatal fevers on a baby’s risk of developing autism – Jun 15, 2017

If you’ve grappled with fevers during the second trimester of your pregnancy, your child could be at an increased risk of developing autism spectrum disorder (ASD), a new study warns.

Columbia University scientists say that expectant moms who encounter a fever over 37.22 C increase their child’s odds of being diagnosed with the developmental condition by 40 per cent compared to women who don’t have a single fever.

Multiple episodes of fever, especially by the second trimester and later, increases the risk even more.

“It’s not that everybody who gets a fever during pregnancy has risk, but the risk is there in a subset. And we think that this may be one of the types of pathways that can raise the risk for autism,” Dr. Mady Hornig, a professor at Columbia University’s Mailman School of Public Health, told Global News.

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“It is a time period, in the second trimester, when all sorts of brain events are happening in the fetus. And so we think that there may be some relationship there,” Hornig said.

READ MORE: 4 misconceptions about autism

This isn’t the first time that scientists have tied fevers to ASD development – other studies have pointed to persistent ailments in pregnancy as a potential pathway. What’s new this time around is the dose-response effect – basically, the more fevers mom deals with, the higher the autism risk.

Hornig even warns that three or more episodes of fever in the latest stages of pregnancy is tied to a 300 per cent increased risk. The idea is that exposure to inflammation even in utero could be disrupting brain development, Hornig said.

WATCH: Why fevers in the second trimester are critical for possible increased risk of autism

Click to play video 'Why fevers in the second trimester are critical for possible increased risk of autism' Why fevers in the second trimester are critical for possible increased risk of autism
Why fevers in the second trimester are critical for possible increased risk of autism – Jun 15, 2017

Research author Dr. Mady Hornig explains why the risk of a baby developing autism is more significant during the mother’s second trimester.

The researchers say that their findings bring the medical community closer to figuring out how to prevent the onset of autism, even in the womb.

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The study is based on data coming out of the Norwegian Mother and Child Cohort study, which followed more than 95,700 women and their children between 1999 and 2009.

READ MORE: 7 fertility myths and misconceptions Canadian women need to know

A notable finding from the research was that none of the women who took ibuprofen to treat their fevers ended up with children who were diagnosed with ASD later on.

This wasn’t the case with acetaminophen, though.

“None of the mothers who took ibuprofen for fever ended up having a child with autism, as compared to women who didn’t take anything in that same trimester for their fever,” Hornig said.

But the study comes with some caveats, though. For starters, not many women in the study were using ibuprofen, so their findings are based on a small sample.

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The study didn’t zero in on what was causing a fever, too. Women could have had microbial infections, flu or other compromising health issues at play that could have been a contributing factor.

One in 68 children fall under the autism spectrum disorder, according to the Centers for Disease Control and Prevention (CDC). The U.S. federal agency says that’s a 30 per cent jump from its last estimate of 1 in 88 children – the latest calculations mean autism is more than twice as common as officials said it was years ago.

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It’s hard to decipher why cases are on the rise but experts say that it could be because of a raised awareness and doctors who can identify cases better now, especially in children with mild problems.

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There are no blood or biological tests for autism. It’s diagnosed by making judgments about a child’s behaviour.

The CDC says that autism affects 1.2 million U.S. children and teens. U.K. health officials say one in every 100 people is living with autism.

Health Canada points to global statistics – “an average prevalence” of about one per cent – but it’s working on a national surveillance system for autism.

Autism affects one out of 42 boys and one in 189 girls, according to estimates.

Hornig’s full findings were published this week in the journal Molecular Psychiatry.

With files from Allison Vuchnich and Veronica Tang