Fever during pregnancy linked to autism risk

By Dr. Ananya Mandal, MDJun 14 2017

According to a new study children born to mothers who have had any kind of fever during pregnancy are at a slightly higher risk of developing and autism spectrum disorder (ASD).

In a large scale study involving thousands of children, an episode of fever during the second trimester (4th through 6th month of pregnancy) has been noted to raise the risk of autism by 40 percent. Several episodes of fever after 12th week of pregnancy (in the second trimester) may raise the risk of autism by three fold, says the study. The study was published on 13th of June in the journal Molecular Psychiatry.

Image Credit: Yuttana Jaowattana / Shutterstock

According to lead researcher Dr. Mady Hornig, associate professor of epidemiology at Columbia University's Mailman School of Public Health in New York City, fever is a response to a myriad of infections and it is fairly common during pregnancy. The absolute risk of fever and autism is low she adds. There are thousands of women who get an episode of fever or flu during their pregnancy, but do not have children with autism. She warned that only an association between fever and autism was found not an absolute “cause and effect” relationship.

For this study the researcher team looked at 95,754 children born at 32 weeks gestation or later children in Norway between 1999 and 2009. Among these, 583 kids went on to develop autism spectrum disorder as identified in Norway through the Autism Birth Cohort Study. The team used logistic regression models to look for associations between fever during in each trimester and ASD risk.

Among mothers of these children, nearly 16,000 reported that they had one or more fevers during pregnancy. This is around 16% which is an average rate of fevers during pregnancy in the United States said Hornig. Having a similar baseline rate of fever means that these rates of autism were not a result of increased number of fevers among pregnant mothers included in the study.

Results showed that the risk for autism rose by 34 percent among mothers who had any fevers during pregnancy. The rates rose by 34% if the fevers occurred in the first trimester or first three months of pregnancy, by 40% if the fevers were seen in the second trimester and by 15% if the fevers occurred in the last trimester or the last three months of pregnancy. Further the risk of autism rose with more number of fever episodes. One or two fevers after the first trimester meant a 1.3 times higher risk. Three or more fevers after the first trimester meant a three times higher risk of autism says the study.

Taking fever medication acetaminophen or Tylenol reduced the risk of autism slightly. Taking Ibuprofen or Advil for the fever did not correlate with autism. This could be due to an association with the drug and reduction of autism or risk or the simple fact that very few women took Ibuprofen for fever during pregnancy said Hornig.

What isn’t clear is the factor in fever that could be the reason for the link. Hornig suggested that the body’s reaction to fever could be the key as this may predict the effects of the body’s reaction to fever or the immune reactions and brain development of the baby the researchers said. Dr. Hornig emphasized that this was not a simple explanation for autism. The actual causative pathway of autism might be more complex.

Autism Spectrum Disorder

ASD is a group of disorders in development of a child that begin in childhood and last through adulthood. In England it is estimated that 1 in every 100 children has an ASD and the CDC estimates for US suggest 1 in 88 children being diagnosed with autism.
Children with autism tend to have problems with social interactions, understanding emotions and feelings of others, problems with language and communication skills and unusual behaviors and patterns of thoughts. There is currently no cure for ASD and treatment involves a wide range of specialist education and behavioural programmes that can help improve symptoms.

Source:  Molecular Psychiatry advance online publication 13 June 2017; doi: 10.1038/mp.2017.119