Study Shows Fever During Pregnancy Increases Risk of Autism at Birth

Researchers at Columbia University in New York have found children born to mothers who experience fever, especially multiple fevers, during the second trimester of pregnancy are at increased risk for developing autism spectrum disorder (ASD). The study analyzed data on 95,754 women participating in the Norwegian Mother and Child Cohort Study that followed pregnant Norwegian women and their children born between 1999 and 2009. They found mothers who experienced a fever above 99 degrees Fahrenheit 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. The chances of ASD rose with the number of maternal fevers, increasing by morethan 300 percent if a mother had three or more fevers after the first trimester.

Mady Hornig, MD, of Columbia University’s Mailman School of Public Health said that sincefever is caused by acute inflammation, a longer exposure of the fetus to an inflammatory environment in the womb may cause a greater disruption of brain development. This increased risk of ASD among women with prenatal fevers has been reported previously, say the researchers, but their study is the first large, prospective investigation showing a so-called doseresponse effect. In addition, their study provides clues about which drug to use during pregnancy to control the fever. This is because not all of the mothers who took the nonsteroidal anti-inflammatory ibuprofen to treat the fever during the second trimester had a child who developed ASD, but mothers who took acetaminophen during that time had very little difference in their child’s fever-related risk for ASD. The researchers note, however, that numbers of women who used ibuprofen during pregnancy are small, so they can’t be confident that ibuprofen had mitigating effects.

“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 Dr. Hornig.

Because the study didn’t address the cause of fever, there is an ongoing study that is “testing blood samples collected at midpregnancy and at birth to explore the possible role of specific infectious agents and the contribution of distinctive patterns of immune response among mothers and children to understand the mechanisms creating vulnerability.”