New Research Explores How Maternal Immune Activity and Pollution May Relate to Autism

A growing body of research is examining how certain prenatal environmental exposures—particularly those affecting maternal immune activity—may relate to neurodevelopment and autism. Three new high-quality studies published in Nature and JAMA Network Open explore these connections while identifying specific biological pathways and exposure windows.

Immune System Changes and Autism

A January 2026 study in Nature analyzing over 100,000 birth records found that changes in maternal immune activity during pregnancy—whether from infections, autoimmune conditions, or general inflammation—were associated with about a 15-20% increase in autism likelihood, similar to the effect size of advanced parental age. The observation was most notable when immune changes occurred during the second trimester, a key period for fetal brain development.

Notably, some studies have found mixed results regarding maternal immune activation, highlighting the need for further research.

Supporting this, a December 2025 Molecular Psychiatry study using rhesus macaque models (n=24) demonstrated that experimentally induced immune activation triggered lasting changes in amygdala development. The researchers identified specific alterations in gene expression patterns that persisted postnatally, potentially relating to social-emotional development.

Pollution and Neurodevelopment

A October 2025 JAMA Network Open study of over 50,000 mother-child pairs found that exposure to fine particulate matter (PM2.5) during pregnancy, especially in the third trimester, was associated with about a 10% increase in autism likelihood after controlling for factors like maternal education, income, smoking status, and pre-existing conditions.

These findings align with a small Nature pilot study (n=86) showing higher levels of certain inflammatory markers (including IL-6 and TNF-α) in maternal blood samples from pregnancies where children were later identified as autistic, particularly in cases with co-occurring intellectual disability.

Understanding Multiple Factors

While the studies note associations, researchers emphasize that autism involves complex interactions between many factors. As The Transmitter explains, most children exposed to these prenatal factors do not develop autism, suggesting other protective or risk factors are involved. The observed associations—while statistically significant—represent relatively small increases in likelihood compared to strong genetic factors.

Notably, some studies have found mixed results regarding maternal immune activation, highlighting the need for further research. The current evidence should be considered alongside the many strengths and valuable neurocognitive differences associated with autism.