A recent study claims that women who take folic acid supplements before conception are at a lower risk of having an autistic child. In Association Between Maternal Use of Folic Acid Supplements and Risk of Autism Spectrum Disorders in Children the authors found that the odds of a child being autistic were 40% lower if the mother took prenatal folic acid supplements. The researchers used the Norwegian Mother and Child Cohort Study(MoBa). A couple of points need to be raised: the report focused on autistic disorder, not ASD’s in general. The number of individuals with Asperger syndrome or PDD-NOS were low, limiting the ability to detect differences. Given that limitation, they found no decreased risk for AS and PDD-NOS with pre conception folic acid supplementation.
Here is part of the abstract:
Results At the end of follow-up, 270 children in the study sample had been diagnosed with ASDs: 114 with autistic disorder, 56 with Asperger syndrome, and 100 with PDD-NOS. In children whose mothers took folic acid, 0.10% (64/61 042) had autistic disorder, compared with 0.21% (50/24 134) in those unexposed to folic acid. The adjusted OR for autistic disorder in children of folic acid users was 0.61 (95% CI, 0.41-0.90). No association was found with Asperger syndrome or PDD-NOS, but power was limited. Similar analyses for prenatal fish oil supplements showed no such association with autistic disorder, even though fish oil use was associated with the same maternal characteristics as folic acid use.
Conclusions and Relevance Use of prenatal folic acid supplements around the time of conception was associated with a lower risk of autistic disorder in the MoBa cohort. Although these findings cannot establish causality, they do support prenatal folic acid supplementation.
The overall prevalence is somewhat low at 0.1-0.2%, but recall that they are focusing on autistic disorder, not ASD’s in general (especially in the abstract). A 40% reduction in autism risk is quite large if real. How does that stack up against other studies? There was a study just last year in the U.S.: Maternal periconceptional folic acid intake and risk of autism spectrum disorders and developmental delay in the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study, which also found a 40% lower risk of autism with Folic acid supplementation. From that abstract:
RESULTS: Mean (±SEM) folic acid intake was significantly greater for mothers of TD children than for mothers of children with ASD in the first month of pregnancy (P1; 779.0 ± 36.1 and 655.0 ± 28.7 μg, respectively; P < 0.01). A mean daily folic acid intake of ≥600 μg (compared with T variant genotypes. A trend toward an association between lower maternal folic acid intake during the 3 mo before pregnancy and DD was observed, but not after adjustment for confounders.
CONCLUSIONS: Periconceptional folic acid may reduce ASD risk in those with inefficient folate metabolism. The replication of these findings and investigations of mechanisms involved are warranted.
One might think this is rather coincidental that two folic acid studies came out so quickly after one another. Or, perhaps not. One study that received a lot of attention in 2009 was Prenatal and Infant Exposure to Thimerosal From Vaccines and Immunoglobulins and Risk of Autism. The study was one of many which showed no increased risk of autism from thimerosal exposure from vaccines. One side finding of the study was published in their technical report: Price C, Robertson A, Goodson B. Thimerosal and Autism. Technical report. They found a possible increased risk due to maternal folic acid supplementation. That study relied upon maternal report, i.e. memory rather than medical records. It would not surprise me if the two recent studies came out of concerns raised by and during the Price study.
What if pre conception folic acid supplementation reduces autism risk? For one thing, this would point again to the prenatal period as important in autism development. Another factor is that this would point out the fact that given the social factors driving up the autism rate, it is very difficult to pull out factors which could be “real” factors driving autism prevalence up–or down as in this case. Folic acid supplementation is a relatively new practice, and still not universal. In the U.S. fewer than 50% of women report taking these vitamins prenatally. But this fraction has increased:
Although year-to-year variation has been observed over time, the percentage of women of childbearing age who reported consumption of a daily supplement containing folic acid increased overall from 28% in 1995 to 32% in 2003 and to 40% in 2004 and 2007
It’s very much a secondary question to whether folic acid supplementation is reducing autism risk, but an interesting question nonetheless.
By Matt Carey