Use of multivitamin or folic acid supplements before or during pregnancy is associated with reduced risk for autism in the offspring, according to an observational study in the Journal of the American Medical Association (JAMA) Psychiatry.

Using Israeli healthcare databases, researchers assessed prescription supplement use in the 9 months before conception and during pregnancy for 27,000 mothers. Of 45,000 offspring, 1% were diagnosed with autism spectrum disorder.

After multivariable adjustment, the risk for autism diagnosis was significantly lower among children born to women who took folic acid and/or multivitamins before pregnancy (relative risk, 0.39) and during pregnancy (RR, 0.27), compared with women who did not supplement. Results were similar when considering folic acid and multivitamin use separately.

The researchers say that epigenetic modifications from supplementation could play a role in the observed association.