Flu And Fever During Pregnancy Boost Autism Risk

Around the world, the incidence of autism has been steadily increasing. This has led scientists to research the possible causes of autism. During one such study, scientists found that autism is associated with fever or flu during pregnancy.

According to the latest statistics, the incidence of autism-related disorders in US children stands at 1 in 88. The rates have shown a steady increase over the last few decades and one pertinent question on everybody’s mind is what the possible causes behind this developmental disorder are.

Scientists have been conducting much research in this field to find some clues about the possible causes behind the increase in autism rates. One such study, conducted by researchers from Denmark and published in a recent issue of the journal Pediatrics, has found that women who suffer from influenza or a febrile episode before the 32^nd week of their pregnancy are more likely to deliver a baby with a high risk of autism spectrum disorders.

A course of antibiotics during pregnancy has also been found to be linked with autism, but the scientists behind the study believe that this association could be purely incidental.

The study involved 96,736 children who were a part of the Danish National Birth Control Cohort (DNBC). All the children in the study were 8 to 14 years old and were born in the period from 1997 to 2003. The mothers of these children were telephonically interviewed about their febrile episodes, history of infections and use of antibiotics, focusing on the gestational period between the 17^th and the 32^nd week. The mothers were again interviewed 6 months after the birth of the child.

The diagnoses of autism spectrum disorder (ASD) in the children were identified as per the Danish Psychiatric Central register. The researchers found that a total of 976 of these children were diagnosed with ASD. This is 1% of the total. Another 342 children were diagnosed with infantile autism, which is roughly about 0.4% of the group.

The risk of both infantile autism and ASD increased marginally if the mother was exposed to macrolides or sulfonamides at any time during her pregnancy. The use of penicillin, particularly during the second and third trimesters was also associated with increased autism risk.

The researchers were unable to find any association between other illnesses in pregnancy like respiratory or sinus infections, and infections of the genitals or the urinary tract, and the incidence of autism in their children.

Other Studies Have Also Found A Link Between Fever And Autism

At least two other studies carried out in the past have found a link between febrile illness in the mother during her pregnancy and an increased risk of ASD in their offspring. 

One such study was the Childhood Autism Risks from Genetics and Environment (CHARGE) study, which was led by Dr. Ousseny Zerbo, a postdoctoral researcher with the Kaiser Permanente Northern California Division of Research, in Oakland, California.

But there's an interesting twist — if the women took medicines such as paracetamol to reduce their fever, there was no increased risk of ASD in their children. However, the CHARGE study was unable to find any correlation between an influenza infection during pregnancy and increased risk of ASD in the offspring.

According to autism researcher Irva Hertz-Picciotto, a professor of environmental epidemiology at the University of California-Davis MIND Institute, who was also a co-author of the CHARGE study, the initial, natural immune response of the body to any infection or injury is inflammation. And inflammation gives rise to fever.

As both her study and the study that followed found an association between fever and the increased risk of developing ASD, it might be possible that inflammation plays a role in causing autism in children. The maternal immune activation during pregnancy may interfere with the proper neurodevelopment of the growing fetus, or so this theory goes.

The hypothesis is purely speculative right now, but it does provide matter for further research.

Although the present study has found some correlation between the usage of antibiotics during pregnancy and the development of ASD in the offspring, the Center for Disease Control and Prevention (CDC) has clarified that the study’s findings are observatory in nature. The new findings should not change the standard clinical recommendations for the treatment of fever and flu in pregnant women. Women should not stop taking antibiotics during pregnancy if they are necessary for treating infections, as there is not enough proof supporting the new findings and infections can be very serious, so antibiotics can be life-saving.

Studies done in the past have found that fever during pregnancy is also associated with structural malformations in the developing fetus, resulting in birth defects. In view of these results as well as the findings of the new study, it is advisable that pregnant women suffering from fever should receive adequate and early treatment.

According to Denise Jamieson, chief of CDC's Women's Health and Fertility Branch, it is also imperative that pregnant women receive flu shots to reduce their risk of getting flu and to slash the risk of serious complications. Influenza symptoms are far more severe in pregnant women compared to non-pregnant women. Moreover, flu shots during pregnancy have positive effects on the baby too. Small babies are too young to get immunization against the flu. Getting a flu shot during pregnancy not only protects the mother but also protects the baby for up to six months.

Autism Spectrum Disorder encompasses a group of developmental brain disorders. According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition- Text Revision (DSM-IV-TR), ASD includes five disorders, namely:

• Autistic disorder (classic autism)
• Asperger's disorder (Asperger syndrome)
• Pervasive developmental disorder not otherwise specified (PDD-NOS)
• Rett's disorder (Rett syndrome)
• Childhood disintegrative disorder (CDD).

Classic autism and Asperger's have since been integrated into a single disorder, Autism Spectrum Disorder, in the DSM-5.

The characteristic symptoms of ASD have been categorized into three main groups:

• Social impairment
• Communication difficulties
• Repetitive and stereotyped behaviors

ASD is four to five times more likely to affect boys. According to the CDCs, more and more children are being diagnosed with ASD than ever before.

ASD is believed to be caused by a number of hereditary and environmental factors. In 9 out of 10 cases, if one of the identical twins has ASD, the other twin also develops symptoms of the disease. Similarly, if one of the siblings in a family has ASD, the chances of other sibling develop the disease are 35 times higher compared to general population.