A report from www.consumerlab.com discussed a recent finding as follows: “Although multivitamin supplementation (3 to 5 times a week) in pregnant women is associated with a reduced risk of autism in their child, excessively high blood levels of folate (>59 nmol/L) in pregnant woman is associated with an approximate twofold increased risk of autism in their child, according to one observational study (Raghavan, International Meeting for Autism Research 2016). The study also found that for pregnant women who had excessive levels of vitamin B-12 (>600 pmol/L are associated with a three fold risk of autism in their child. …for pregnant women who had excessive blood levels of both folate and vitamin B-12, the risk was 17.6 times greater.”
This information may be an interesting clue, but at this point I would not recommend pregnant women, or women planning a pregnancy, make any changes in their supplementation regimen unless they first discuss their questions with their obstetrician. This information is fodder for important discussions between patient and physician. Educated patients have the best outcomes.