Prenatal folic acid and multivitamin supplementation and offspring autism risk: umbrella-ified review

"Maternal prenatal folic acid and multivitamin supplementation are associated with a reduced risk of ASD [autism spectrum disorder] in offspring. These findings have important public health implications, suggesting that prenatal supplementation could help mitigate the risk of ASD in children." https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0334852

The results of an umbrella review that included 8 other systematic reviews or meta-analyses which themselves included over 100 studies which included several million mother-child pairs. In short, top tier evidence.

"Prenatal folic acid and/or multivitamin supplementation was associated with a 30% reduced risk of ASD in offspring (RR = 0.70, 95% CI: 0.62, 0.78; GRADE: highly suggestive). Subgroup analysis by supplement type showed that maternal prenatal multivitamin supplementation reduced the risk of ASD by 34% (RR = 0.66, 95% CI: 0.55–0.80; GRADE: highly suggestive), while folic acid supplementation was associated with a 30% reduction in ASD risk (RR = 0.70, 95% CI: 0.60–0.83; GRADE: highly suggestive)."

And yet again, folate metabolism and autism. 

The same folate metabolism and autism that is also US health policy now in terms of some autisms being potentially linked to cerebral folate deficiency (CFD) and/or folate receptor autoantibodies (FRAAs) meriting use of leucovorin (folinic acid). The difference being that in those areas - CFD and FRAAs - folic acid may not be the optimal supplement to use, as per why folinic acid (and perhaps even methylfolate) is instead being suggested for some children/adults with autism. Whether that might also translate into similar issues with folate metabolism for mums-to-be too as, being a risk factor for offspring autism, remains to be seen.

Nutritional factors being important to at least some autisms? Who'd have thunk that?