Children whose mothers had any type of fever while pregnant may be at slightly higher risk of developing autism.  The chances of a child developing autism are highest if the fever occurs in the second trimester, but are still fairly low.  There was found to be only a 40% greater chance of the unborn child developing autism, and an even lower risk if the fever occurred during the first or third trimesters.  However, women who had three or more fevers after their twelfth week of pregnancy were about three times more likely than average to have a child with autism.  

At this point, researchers are unsure if the fever itself is a cause of autism, or if there is simply a correlation between the two.  None of the women studied who took ibuprofen during pregnancy had a baby with autism; however, the number of women who took ibuprofen was so small that it may be insignificant.