Children born to mothers who experienced fever, especially multiple fevers, during the second trimester of pregnancy are at increased risk for developing autism spectrum disorder (ASD), a new study suggests. Researchers found that mothers who experienced a fever over 99 degrees F (37.22 C) during the second trimester of pregnancy had a 40 percent increased risk of having a child with ASD compared to women who had no fevers.
But none of the women who used ibuprofen to treat a fever during pregnancy gave birth to children later diagnosed with autism, the researchers note. "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," said lead author Dr Mady Hornig of Columbia University's Mailman School of Public Health in New York. An increased risk of ASD among women with prenatal fevers has been reported before, the authors write in the journal Molecular Psychiatry. What's new about this study is that it is the first large, prospective investigation showing a so-called dose-response effect.
The chances of ASD rose with the number of maternal fevers, increasing by more than 300 percent if a mother had three or more fevers after the first trimester. Since fever is caused by acute inflammation, the profound difference in risk of ASD is consistent with the idea that a longer exposure of the fetus to an inflammatory environment in the womb can cause a greater disruption of brain development, said Hornig. A crosstalk of immune molecules called cytokines can reach the fetus across the placenta to affect the developing brain.