A woman in a hospital bed

Hospitalized pregnant women who were diagnosed with an infection are more likely to have a child with autism.

A study from health care provider Kaiser Permanente’s Division of Research contributes to the mounting evidence linking immune system activity during pregnancy to a child’s later development of an autism spectrum disorder (ASD). The study analyzed the association between pregnant women being diagnosed with an infection while in the hospital and children later being diagnosed with an ASD. They found that pregnant women who are diagnosed with a bacterial infection while hospitalized are more likely to have a child with an autism spectrum disorder.

The researchers evaluated data from 407 children with an ASD and 2,075 demographically-matched children without an ASD. The children were born between January 1995 and June 1999 to mothers who were part of the Kaiser Permanente system during and for at least two years after the child’s birth. The research team searched for records of mothers being diagnosed with bacterial infections—of the urinary tract or amniotic fluid, for example—comparing it to later data regarding the diagnosis of an ASD.

Dr. Lisa Croen, senior study author, explains the findings: “Only bacterial infections diagnosed in the hospital were associated with an increased risk. Infections diagnosed in a hospital setting were more common among mothers of children who developed an ASD compared with mothers of children who did not develop an ASD.”

The results were that women diagnosed with a bacterial infection had a 58 percent greater risk of having a child with an ASD. Infections were not as common among mothers of children who did not have autism; 1.5 percent of mothers of a child with ASD had infections, compared to just 0.5 percent of mothers of children without an ASD. Finally, infections during the second trimester of pregnancy were correlated to a three-fold increase in risk of developing an ASD.

Although this research strengthens the link between a pregnant woman’s immune system activity with the later diagnosis of a child with autism, the researchers admit that the exact mechanism for this relationship is not yet known. Ousseny Zerbo, Ph.D. and lead author of the study posits that the severity of the infection may be related to the increased risk of ASD.

Most infections during pregnancy are not associated with an autism risk.

This research is published in the Journal of Autism and Developmental Disorders.

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