While genetics account for the majority of autism risk, environmental factors during pregnancy and early life may also play a role. Research has identified several environmental associations, though none has been shown to independently cause autism.

Prenatal Factors

Advanced parental age at conception is one of the most consistently replicated environmental risk factors. Maternal infections during pregnancy, particularly those causing high fever, have been associated with modestly increased risk. Air pollution exposure during pregnancy has also been linked to autism in some studies, though the effect sizes are small.

Pregnancy Complications

Gestational diabetes, preeclampsia, and other pregnancy complications have shown small associations with autism risk. Preterm birth and low birth weight are also modest risk factors. These complications may affect fetal brain development during critical periods.

Gene-Environment Interaction

Environmental factors likely increase autism risk only in genetically predisposed individuals. The same environmental exposure may have no effect on one child while contributing to autism in another based on their genetic background. This explains why no single environmental factor causes autism consistently.

What This Means for Families

These associations should not cause guilt or anxiety. Environmental risk factors identified in research are generally common experiences that most people cannot or should not avoid. The most productive focus is on early identification and intervention. If you have concerns about your child’s development, contact your pediatrician for screening.