Scientists continue to dig deep for the cause of one of the most common special-needs conditions: the autism spectrum disorder (ASD). Currently, there is no known cause for ASD. But many experts believe that it is a genetic condition that develops during early pregnancy from a combination or multiple factors (genetics, parents’ age, and environmental toxins, among others).
Recently, a new study, published in the journal Molecular Psychiatry, has found an association between fever during pregnancy and ASD. It is one of the largest research conducted to date, following 95,754 children born between 1999 and 2009 in Norway, including 583 children who were diagnosed with some form of autism. More than 15,701 mothers had fever once or more during the whole nine months.
"Our results suggest a role for gestational maternal infection and innate immune responses to infection in the onset of at least some cases of autism spectrum disorder,” study lead author Dr. Mady Hornig, associate professor of Epidemiology and director of Translational Research at Center for Infection and Immunity (CII), said in a statement.
The researchers found that children whose moms had a fever over 37.22 degree-Celsius at any point in the pregnancy had 34-percent higher risk of developing ASD.
Researchers from the Columbia University's Mailman School of Public Health in New York said the link between fever and ASD appears to be stronger if the mom had it during her second trimester of pregnancy. The results show that they were 40 percent more likely to have kids who developed the condition. What's more, the risk of the children being diagnosed with autism is even higher, up at 300 percent, when the mom had fever three or more times after the first trimester.
"What is particularly important about our findings is that it not only strengthens the evidence for a particular pathway for ASD, but it also suggests that we may be very close to understanding how to safely mitigate or prevent some outcomes by directing prevention or intervention strategies toward this pathway," Dr. Hornig told Reuters.
Fever is merely a symptom -- it's one of the bodies ways to fight an infection.Fevers during pregnancy are not unheard of or particularly alarming, senior study author W. Ian Lipkin, professor of Epidemiology and director of CII, told NBC News. He suspected it’s the mother's immune response that's causing the damage, not the fever per se or the kind of infection.
It may be that inflammatory chemicals such as cytokines are crossing the placenta and affecting the developing brain of the fetus, Lipkin explained. Hornig suggested that a longer exposure of the fetus to an inflammatory environment in the womb can cause a greater disruption in brain development.
The study also looked into anti-fever medication -- acetaminophen and ibuprofen (no mention was made of paracetamol) -- to address that risk. The researchers found the mothers who took acetaminophen to lower their fever during the second trimester were only slightly less likely to have kids with ASD.
However, none of the children born to moms who took ibuprofen after the first trimester developed ASD. That said, not many pregnant women in the study used ibuprofen because it’s also linked to other pregnancy risks. The researchers could not definitively make suggestions how to best manage fever during pregnancy based on their data.
What’s important to note is the research isn’t saying fever causes autism, but the findings show a link. While it is the first study to investigate a dose-response effect or exposure-response relationship, the researchers believe fever, while it could be a factor, is not likely working alone.
"There is something in the mother's immune response that may increase the risk for the baby," Dr. Hornig told WebMD. "But it's not for every mother. We don't think this is a pathway for autism. We don't think it's the only way autism is triggered in children."
There’s already an ongoing study to test blood samples collected mid-pregnancy and at birth to explore the possible role of specific infectious agents and distinct patterns of immune response in mothers and children. It hopes to shed light on what makes the baby vulnerable to infection or immune response.
Read more about how you can avoid getting sick while pregnant here.