Folic Acid Supplementation Linked to Reduced Autism Risk

A study including more than 80,000 Norwegian children finds that folic acid supplementation early in pregnancy is associated with a 40% reduction in the risk of developing severe autism.

Women who take folic acid supplements early in pregnancy appear to have a significantly lower risk of having a child with severe autism, according to the results of a study published in the February 13, 2013, edition of the Journal of the American Medical Association. The study was carried out using a sample drawn from the population-based, prospective Norwegian Mother and Child Cohort Study (MoBa).

Folic acid supplements taken during pregnancy are already generally understood to reduce the risk of having a child with neural tube defects, and women are generally advised to take the supplements beginning a month before conception. A previous study drawing on the MoBa sample found that folic acid supplementation was associated with a reduced risk of severe language delay at age 3.

The current study included 85,176 children born between 2002 and 2008. At the end of follow-up in March 2012, the children ranged in age from 3.3 to 10.2 years. At this point, 270 children in the study had been diagnosed with autism spectrum disorders (ASDs): 114 (0.13%) with autistic disorder, 56 (0.07%) with Asperger syndrome, and 100 (0.12%) with pervasive developmental disorder—not otherwise specified (PDD-NOS).

Of the children in the study, 61,042 were born to mothers who took folic acid supplements at some point between 4 weeks before conception and 8 weeks after conception, and 24,134 were born to mothers who did not take folic acid supplements at all during this period. The researchers focused on this period in pregnancy because it includes the closure of the neural tube and the development of basic brain structures in the child.

The researchers found that 0.10% of children whose mothers took folic acid supplements during this period were diagnosed with autistic disorder, the most severe form of ASD, compared with 0.21% of children whose mothers did not take the supplements. After adjusting for a range of confounding variables, the researchers determined that the adjusted odds ratio for developing autistic disorder in children whose mothers took folic acid supplements early in pregnancy was 0.61.

There was, however, no association found between maternal folic acid supplementation in the middle of pregnancy and the likelihood of a child developing autistic disorder. Nor was any significant association found between maternal use of folic acid supplements early in pregnancy and the likelihood of a child developing Asperger syndrome or PDD-NOS. In addition, there was no association found between maternal use of fish oil supplements and the likelihood of a child developing autistic disorder, although fish oil use was associated with similar maternal characteristics to folic acid supplementation.

The researchers conclude that their results add further support for advising women to take folic acid supplements early in pregnancy. They note that women who took folic acid supplements during pregnancy tended to be of higher socioeconomic status and to be more health-conscious, so it is possible that some of the reduction in risk of autistic disorder they found was due to unmeasured confounding. However, the lack of an association between fish oil supplementation anytime during pregnancy or folic acid supplementation in the middle of pregnancy and reduced rates of autistic disorder suggests that this is not the case.