Micronutrient supplementation was linked to lower autism rates in an analysis of more than 3 million pregnancies. Digest
Autism spectrum disorder affects around one percent of children worldwide and has few established preventive strategies. A new synthesis of existing research examined whether commonly recommended prenatal supplements might influence this risk by comparing autism diagnoses in children whose mothers did or did not take them.
Researchers in Australia carried out an umbrella review, a study that reanalyzes findings from multiple systematic reviews and meta-analyses. They identified eight reviews covering 101 primary studies and more than three million mother-child pairs worldwide. The team compared autism spectrum disorder rates in children according to whether their mothers used supplements before or during pregnancy, looking separately at two exposures: folic acid and multivitamin preparations.
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Here is what the researchers observed:
- Six of the eight reviews found protective associations between prenatal supplements and autism, while two reviews, one addressing folic acid and one addressing multivitamins, reported no clear link.
- Across all included data, maternal use of folic acid and/or multivitamins during pregnancy was associated with about a 30% lower likelihood of a child receiving an autism diagnosis compared with no supplementation.
- When analysis was limited to multivitamin products, supplementation corresponded to roughly a 34% reduction in autism risk.
- Folic acid use on its own showed a similar association, with children of supplemented mothers experiencing around a 30% lower risk of autism than those whose mothers did not take folic acid.
These findings align with current knowledge about nutrient effects on brain development. Multivitamins supply extra vitamins and minerals that help neurotransmitter production and neuron maturation. Folic acid helps run the chemical pathways needed for early brain and spinal cord development. Importantly, some people carry genetic variants that slow the body's ability to activate folic acid, which can lead to unmetabolized folic acid buildup and lower levels of usable folate, a pattern linked to poorer pregnancy-related outcomes. 5-methyl-folate, which is also available as a supplement, does not rely on this conversion step.
Taken together, this work reinforces guidance to ensure adequate micronutrient intake before and during pregnancy and suggests that standard supplements may help lower autism risk. Even so, this umbrella review uses mainly observational data, so it cannot prove that supplementation prevents autism. Future studies must clarify who benefits and how best to use these products. In Aliquot #100, I discuss factors that influence child development before conception, during pregnancy and infancy, and into the toddler and early childhood years.