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Fever during pregnancy may raise the risk for autism spectrum disorder (ASD) in the child. The effect was high in the second trimester, raising odds for ASD by 40 percent.
Risk of an ASD was increased by over 300 percent for the children of women reporting three or more fevers after four months of pregnancy.
The researchers followed 95,754 children born between 1999 and 2009, including 583 cases of ASD identified in Norway through the Autism Birth Cohort (ABC) Study.
Mothers of 15,701 children (16 percent) reported fever in one or more four-week intervals throughout pregnancy, similar to rates reported in the U.S. ASD risk was increased by 34 percent when mothers reported fever at any time during pregnancy, and by 40 percent in the second trimester.
The risk increased in a dose-dependent fashion from 1.3-fold with one or two fever episodes after the twelfth prenatal week to 3.12-fold with three or more.
Gestational maternal infection and innate immune responses to infection in the onset of pregnancy can increase some cases of autism spectrum disorder.