Women who take folic acid and/or multivitamin supplements before and/or during pregnancy appear to lower the risk of their children having autism spectrum disorders (ASD), according to a multinational study published January 3 in the American Medical Association journal JAMA Psychology.

The findings have “important public health implications” according to the authors of the study, which was led by Stephen Z. Levine and Dr. Arad Kodesh of the University of Haifa’s Department of Community Mental Health, with Alexander Viktorin of the Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai in New York and the Department of Medical Epidemiology and Biostatistics at Karolinska Institute in Stockholm.

The case-controlled cohort study – using data from Meuhedet, one of Israel’s four national HMOs — involved 45,300 Israeli children (22,090 girls and 23,210 boys) born between January 1, 2003, and December 31, 2007 and who were later diagnosed with ASD, compared to a control group from a random sampling. Data on vitamins purchased by their mothers was extracted from Meuhedet’s pharmaceutical registry.

Vitamin supplements were classified for folic acid (vitamin B9), multivitamin supplements (vitamins A, B, C and D), and any combination thereof, taken by the mothers in the intervals before and during pregnancy.

“Maternal exposure to folic acid and/or multivitamin supplements before pregnancy [and/or during pregnancy] was statistically significantly associated with a lower likelihood of ASD in the offspring compared with the offspring of mothers without such exposure,” according to the report. “The results generally remained statistically significant across sensitivity analyses.”

Previous studies on the specific link between vitamins, folic acid and autism have had inconsistent results, and the authors of the current study state that the reason for the association they observed remains unclear.