Prenatal Folic Acid Supplements and Offspring's Autism Spectrum Disorder: A Meta-analysis and Meta-regression.

The included studies were observational, meaning they cannot prove that folic acid supplements caused the reduction in ASD risk; other factors related to maternal health or socioeconomic status may explain the association. Recall bias was present in many studies where supplement use was self-reported via questionnaires rather than verified through prescription records. Results varied significantly by geographic location, with no protective effect seen in European or Chinese populations, suggesting that factors like baseline dietary folate or genetic differences may influence the outcome. The quality of evidence was mixed, with only one study rated as high quality and one as low quality; the remaining eight were moderate. The analysis did not account for potential U-shaped risk curves, where very high or very low folate levels might both be associated with increased risk, as noted in some cited literature but not fully explored in the meta-analysis itself.

The study was funded by the Science and Technology Department of Guangdong Province, the Guangzhou Institute of Pediatrics, the Ministry of Science and Technology of China, and the Guangzhou Municipal Health Commission. No specific commercial conflicts of interest regarding folic acid manufacturers were declared in the provided text.

Do not interpret this as proof that folic acid supplements prevent autism. The evidence comes from observational studies with significant geographic variability and potential confounding factors, and the lack of effect in some populations suggests the relationship is not straightforward or universally applicable.