Serious infections in pregnant women increase the child's risk of developing autism

Physicians are investigating the connection between severe infections and autism
If expectant mothers contract a serious infection during their pregnancy, which requires hospitalization for treatment, this increases the child's risk of developing autism.

Researchers at the internationally recognized Massachusetts Institute of Technology (MIT) and the University of Massachusetts Medical School have found in their study that severe maternal infections during pregnancy increase the risk of developing autism in their children. The doctors published a press release on the results of their study.

If mothers suffer a serious infection during pregnancy, it increases the likelihood that their children will develop autism. (Image: nerudol / fotolia.com)

Pregnant mother infections can cause brain changes in the child
In a study on mice, the experts found that infections can affect the composition of bacterial populations in the digestive tract of the mother. In their study, the scientists wanted to find out whether a maternal infection during pregnancy leads to autistic behaviors in their offspring. They also discovered specific brain changes that produce such behaviors.

Scientists identify brain region involved in autistic-like behaviors
"We were able to identify a brain region that is involved in all behaviors associated with this disorder," explains author Professor Gloria Choi. If these findings are confirmed in human studies, the findings could provide a clue to reduce the risk of autism. This would involve blocking the function of certain bacterial strains in the maternal intestine, the researchers explain.

How do infections affect the child during pregnancy??
A 2010 study, which included all Danish-born children born between 1980 and 2005, noted even then that severe viral infections during the first trimester of pregnancy lead to a threefold increased risk of autism. Second-trimester severe bacterial infections were also associated with a 1.42-fold increase in risk. The infections involved included influenza, viral gastroenteritis and severe urinary tract infections, the experts add.

Special immune cells are involved in the increased risk
Similar effects were also found in experiments on mice. A special type of immune cells (called Th17 cells) and their effector molecule IL-17 are responsible for these effects. IL-17 then interacts with receptors found on the brain cells of developing fetuses. This leads to irregularities in certain parts of the cortex. In the current investigation, the doctors tried to find out more about these irregularities. So they wanted to determine whether the irregularities are responsible for the behavioral anomalies found in the affected mice. The researchers found that the irregularities occur in a part of the brain called the S1DZ. The irregularities reduce the populations of cells, also referred to as interneurons.

Physicians were able to reverse behavioral anomalies
When the researchers restored normal brain activity in this area, they were able to reverse the behavioral abnormalities that occurred. They were also able to induce behavioral abnormalities in otherwise normal mice by strongly stimulating SIDZ neurons. The S1DZ region sent messages to two other brain regions, called the temporal association region of the cortex and the striatum. By inhibiting neurons associated with the temporal association region, the researchers were able to reverse societal deficits that occurred. By inhibiting the neutrons associated with the striatum, they were able to terminate repetitive behavior.

Inflammation during pregnancy is only one reason for behavioral abnormalities
Not all mothers who experience a serious infection get a child with autism and not all mice in the attempted inflammation-developed behavioral disorders. This suggests that inflammation during pregnancy is only one of the factors responsible for behavioral problems. The data from the study shows that only the offspring of mice with a certain type of harmless bacteria developed behavioral disorders and irregularities in parts of the cortex. When the researchers killed these bacteria with antibiotics, the mice gave birth to normal offspring. These data suggest that perhaps only certain mothers carrying these types of Th17 cell-inducing bacteria in their intestines may be susceptible to this inflammation-induced disease. (As)