Brain & NeuroscienceResearch
New Insights into How Maternal Immune Activation During Pregnancy May Influence Autism Risk
Groundbreaking studies reveal lasting biological impacts of prenatal immune responses, while air pollution data remains complex
The Immune Connection
A growing body of research confirms that when a pregnant person's immune system is activated by infections or inflammation, it may influence fetal brain development in ways that increase autism likelihood. A 2026 review in Nature analyzed birth cohort data from over 100,000 children, finding consistent associations between maternal immune activation (MIA) and later autism diagnoses.
What's particularly striking is new evidence about how this process works biologically. A December 2025 study in Molecular Psychiatry using primate models showed that MIA causes lasting changes in how genes are expressed in the amygdala - a brain region involved in emotional processing. These changes were detectable long after birth, suggesting prenatal immune activity may have enduring effects on brain development.
Environmental Factors and Biomarkers
Researchers are also making progress in identifying measurable signs of this process. Altered immune molecules in both maternal blood during pregnancy and umbilical cord blood at birth have shown promise as potential predictive markers, according to findings cited in a PubMed review.
Air pollution remains another area of interest, though the picture is complex. While prenatal exposure to fine particulate matter (PM2.5) has been associated with autism risk in multiple studies, a 2025 JAMA Network Open study found postnatal ozone exposure might have stronger effects - highlighting how different environmental factors may operate through distinct biological pathways.
The Big Picture
What emerges from these studies is an understanding of autism risk as shaped by multiple interacting factors. Genetic predisposition matters, but so does the prenatal environment - with maternal immune activation appearing to play a particularly important role. As research continues, scientists hope to better understand these complex interactions, potentially leading to improved supports and interventions.
Sources
- 01Prenatal and birth factors associated with child autism diagnosis: a birth cohort perspective
- 02Prenatal maternal immune activation triggers lasting cell-specific transcriptomic dysregulation in the amygdala of primate offspring | Molecular Psychiatry
- 03A critical prenatal risk factor for autism spectrum disorder - PubMed
- 04Prenatal Exposure to Fine Particulate Matter Components and ...
Behind the brief
Adversarial editorial review
Open thread