Researchers have found more evidence that inflammation during early pregnancy increases autism risk. The new study found high autism rates among children born to mothers with elevated levels of C-reactive protein (CRP). High CRP is an established marker of body-wide inflammation.
“Elevated CRP is a signal that the body is undergoing a response to inflammation from, for example, a viral or bacterial infection,” says study leader Alan Brown, M.D. “The higher the level of CRP in the mother, the greater the risk of autism in the child.” Dr. Brown is a professor of clinical psychiatry and epidemiology at Columbia University College of Physicians and Surgeons, the New York State Psychiatric Institute and the Mailman School of Public Health.
The analysis found that autism risk increased by 43 percent among children of mothers with CRP in the top 20th percentile. This means that their CRP levels were higher than 80 percent of those tested. Autism risk increased by 80 percent among children of mothers with CRP in the top 10th percentile (higher than 90 percent of those tested).
The findings add to mounting evidence that an overactive immune response can alter brain development during pregnancy. However, Dr. Brown emphasizes that the vast majority of mothers with increased CRP levels will not have children with autism.
“We don’t know enough yet to suggest routine testing of pregnant mothers for CRP for this reason alone,” he says. “However, exercising precautionary measures to prevent infections during pregnancy may be of considerable value.”
Dr. Brown’s team analyzed information from the Finnish Maternity Cohort. This national biorepository contains blood samples collected during early pregnancy from more than 800,000 women. Finland also maintains a national registry of children diagnosed with autism.
This allowed the researchers to analyze CRP in pregnancy blood samples from mothers of 677 children with autism. For comparison, they also looked at samples from an equal number of pregnant women whose children did not develop autism. The strong link between elevated CRP and autism risk was not associated with parental age, previous births, socioeconomic status, preterm birth or birth weight.
“While research has shown that maternal infection is a risk factor for autism, this is the first study to identify a biomarker of that infection during pregnancy,” adds Alycia Halladay, Ph.D., Autism Speaks senior director of environmental and clinical sciences. “Future studies may help explain how infections or other inflammatory events during pregnancy interact with known autism risk genes,” she says. “Such studies may also lead to protective intervention measures.”