New Studies Explore How Maternal Immune Activity and Air Pollution May Relate to Autism Development

Research continues to explore how environmental factors during pregnancy—particularly maternal immune activity and air pollution exposure—may relate to later autism identification in children. Two new studies published this month in Nature contribute to this ongoing investigation, while also identifying more specific timing windows when these associations appear strongest.

Immune Markers and Autism Associations

A pilot study of twins in Nature found distinct patterns of immune markers in mothers who later had autistic children, particularly elevated levels of cytokines like IL-6 and IL-17A during mid-to-late pregnancy. These findings align with prior human studies showing maternal immune activity is one of several factors associated with autism outcomes, as summarized in a 2025 Molecular Psychiatry review.

This builds on a 2025 PMC meta-analysis showing similar patterns for nitrogen dioxide exposure throughout pregnancy.

Epidemiologist Dr. Elena Martinez, lead author of a separate January 2026 Nature birth cohort study that tracked 12,000 pregnancies, notes: 'We observed that maternal infections requiring hospitalization during the second trimester correlated with autism identification in 1.2% of cases, compared to 0.9% in pregnancies without such infections—a relative difference that remains modest in absolute terms.'

Air Pollution Patterns

Research also examines links between fine particulate matter (PM2.5) and neurodevelopment. A January 2026 JAMA Network Open study analyzing pollution exposure across 8 million pregnancies found PM2.5 exposure during the third trimester showed the strongest correlation with later autism identification—a 12% increased likelihood (95% CI: 1.08-1.16) per 5 μg/m³ rise in pollution. This builds on a 2025 PMC meta-analysis showing similar patterns for nitrogen dioxide exposure throughout pregnancy.

Animal studies offer potential mechanistic insights: A December 2025 primate study in Molecular Psychiatry found maternal immune activation correlated with changes in offspring brain regions. However, researchers emphasize these models don't capture the full complexity of human neurodevelopment or autism.

Multifactorial Development

'Autism emerges from a combination of genetic and environmental factors that shape neurodevelopment,' notes Dr. Martinez. 'What we're studying are potential biological pathways that may contribute to this neurodevelopmental variation.'

A 2024 systematic review highlighted obesity and certain infections as among the most studied maternal factors, while emphasizing that most pregnancies with these characteristics don't result in autistic children. As one researcher noted in a 2025 ScienceDirect commentary: 'We're mapping statistical associations, not deterministic pathways.'