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Autism Linked to Allergic Disease During Pregnancy?

Action Points

  • Reassure concerned expectant mothers that these results are extremely preliminary and, despite what the media reports, even the researchers themselves concluded that asthma and allergic disease in pregnant women are unlikely to contribute significantly to autism risk.
  • Review the new federal guidelines, updated last month, on managing asthma during pregnancy at http://www.nhlbi.nih.gov/health/prof/lung/asthma/astpreg.htm.

There appears to have been an increase in the number of cases of autism diagnosed in the United States and other parts of the world over the last 20-30 years. Much of this trend is accounted for by increased awareness of autism. Studies have suggested the presence of a strong genetic component. However, epidemiologic studies have continued to look for potential nongenetic factors and gene-environment interactions.

Previous studies have suggested a link between a family history of autoimmune disorders and autism, but these studies relied largely on unverified self-reports from self-selected participants.

Therefore, Lisa A. Croen, a researcher from Kaiser Permanente in Oakland, California, and colleagues took a more rigorous approach in investigating the association between autism and a history of maternal autoimmune diseases, allergies, and asthma.

The researchers hypothesized that a maternal immune response during pregnancy might affect fetal brain development in genetically susceptible individuals.

The case-control study compared 407 children ages 3 to 7 with autism to more than 2,000 control cases. Diagnoses of more than 40 different autoimmune diseases, asthma, and allergic diseases in the mothers during the 4 years surrounding pregnancy and delivery were gathered from inpatient and outpatient databases. (However, the researchers were careful to point out that these diagnoses were not confirmed by a clinical examination or review of medical records.)

Statistical analysis yielded the following key results:

  • After adjusting for other factors, only one autoimmune condition, psoriasis, was significantly associated with autism (adjust odds ratio [OR], 2.7; 95% CI 1.3-5.8).

  • A more than 2-fold increased risk was seen for maternal asthma and allergy diagnosis during the second trimester of pregnancy. However, the results, while statistically significant, were not especially strong. For asthma, OR=2.2; 95% CI 1.1-4.2. For allergy, OR=2.5; 95% CI 1.2-5.2.

The researchers interpreted their results cautiously: "These findings suggest that maternal autoimmune disorders present in women around the time of pregnancy are unlikely to contribute significantly to autism risk," they concluded. "Further etiologic investigations are needed to confirm these results and should include objective documentation of diagnoses and consider a larger set of maternal immune-related conditions, including asthma and allergies."

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