Women who take multivitamins and folic acid before or during pregnancy are significantly less likely to have a child who will develop autism spectrum disorder (ASD), according to researchers.

Of 45,300 Israeli children born between 2003 and 2007 who took part in the study, 572 were diagnosed with ASD, equating to 1.3% of children. The study involved 22, 090 girls and 23, 210 boys who were assessed for ASD in 2015.

Researchers concluded: “Maternal exposure to folic acid and multivitamin supplements before and during pregnancy is associated with a reduced risk of ASD in the offspring compared with the offspring of mothers without such exposure.”

Commenting on the study which was published in JAMA Psychiatry, Dr Carrie Ruxton from the Health and Food Supplements Information Service, said: “The results showed a 61% reduced risk of autism when mothers had taken either a multivitamin and/or folic acid supplement prior to becoming pregnant.

“It was also found that mothers who took these vitamin supplements during pregnancy were 73% less likely to have a child who went on to be diagnosed as autistic. While this is an observational study and we need to be cautious, it is an important finding which contributes to our body of knowledge on factors linked with autism.

“Around 75% of women of childbearing age in the UK have an inadequate folate status putting their children at risk of neural tube disorders, such as spina bifida.

“Only a quarter of women take the recommended folic acid supplements before conception and in the first trimester of pregnancy. It is possible, given these new findings, that a lack of key nutrients may also be an issue for autism risk.”