Maternal Infection During Pregnancy Raises Risk of Autism in Children

Scientists may have uncovered a new risk factor when it comes to autism. They've discovered that hospital-diagnosed maternal bacterial infections during pregnancy were associated with an increased risk of autism spectrum disorders in children. The findings contribute to a growing body of work on the role of infection in autism risk.

In order to better understand the role that infection might play in autism, the researchers examined 407 children with autism and 2,075 matched children who did not have autism. These children were all born between January 1995 and June 1999.

"Though infections in pregnant women are fairly common, in this study most were not associated with an increased risk of autism," said Lisa Croen, one of the researchers, in a news release. "Only bacterial infections diagnosed in the hospital were associated with an increased risk. Infection diagnosed in a hospital setting was more common among mothers of children who developed an ASD compared with mothers of children who did not develop an ASD."

In fact, the researchers found that women with bacterial infections diagnosed during a hospitalization had a 58 percent greater risk of having a child with an ASD. While not very common in any of the mothers studied (1.5 percent of mothers of a child with ASD vs. .5 percent of mothers of a child without ASD), infections diagnosed during a hospitalization in the second trimester were associated with children having more than a three-fold increased risk of developing ASD.

Currently, researchers haven't established exactly what the mechanism is for how maternal infections may influence autism risk. Yet there is a clear association between the two. In addition, animal tests have shown that immune-system responses to infections during pregnancy may influence the neurological development of the fetus.

"Our findings indicate that although most infections during pregnancy were not associated with autism in the child, there appears to be some increased risk for autism," said Ousseny Zerbo, one of the researchers, in a news release. "It would be prudent for pregnant women to contact their doctor if they suspect an infection."

The findings are published in the Journal of Autism and Developmental Disorders.