The study examined the incidence of autism in over 85,000 children born in Norway between 1999 and 2009. Questionnaires completed by the mothers indicated how much folic acid they’d consumed in the month prior to becoming pregnant and over the first eight weeks of pregnancy, a period critical in embryonic brain development. A total of 270 out of 85,176 children developed an autism spectrum disorder (0.32 percent). The most debilitating of these, autistic disorder, occurred in 56 children (0.07 percent), and 100 children (0.12 percent) developed Asperger syndrome. For comparison, autism spectrum disorders occur in about 1 percent of children.
The raw data showed that mothers who did not take folic acid supplements during pregnancy showed a more than 2.1-fold chance of having children born with autistic disorder compared to mothers who took folic acid. However there were other factors that may account for the difference that have nothing to do with taking folic acid. Mothers who were more likely to take folic acid supplements were also more likely to have gone to college, were less likely to be smokers, and more likely to be first-time mothers who had planned their pregnancies. Taking these into account, the researchers concluded that taking folic acid still decreased risk of having a baby with autistic disorder by 39 percent. The data also showed a lower chance for having a baby born with Asperger syndrome, but the difference was not statistically significant when the above factors were considered. And indicating that folic acid affects brain development during the critical period, data showed that taking folic acid later in pregnancy did not affect the chances of having a child with autism spectrum disorder.But it’s also possible that the lower risk in mothers that took folic acid before and during pregnancy is due to differences in other health behaviors. To control for this, the researchers repeated their analysis and compared outcomes between mothers who took fish oil supplements and those who did not, working with the assumption that the health behavior differences between those who took folic acid or not were the same between those who took fish oil or not. Confirming the differences were due to folic acid, they found no association between fish oil and risk for autism spectrum disorders.
The study was conducted by scientists at the Norwegian Institute of Public Health and published in the Journal of the American Medical Association.
So how could taking folic acid during pregnancy affect whether or not the child is born with autism? Scientists aren’t sure, but the role the vitamin plays in the cell might lend a clue. Folate – and its synthetic form, folic acid – provides the body with 1-carbon units necessary for basic cellular processes including DNA replication and modifying DNA, RNA and protein. It’s possible that changing the timing or efficacy of these processes might tip the balance between normal and abnormal neuronal network formation during the critical period of brain development.
Supporting the idea that taking folic acid during pregnancy is good for the unborn baby’s developing brain is a 2011 study that showed folic acid supplements taken four weeks before to eight weeks after conception was associated with a decreased risk of severe language delay in 3-year-old children. And another study showed that prenatal folic acid or iron supplements were associated with higher intellectual scores when the children had reached 7 to 9 years of age.
Autism spectrum disorders, as the name indicates, are complex conditions the cause of which continues to elude scientists. It is estimated that the disorders are about 90 percent hereditary. And exactly which genes make it hereditary was recently elucidated upon in a study that uncovered 24 new genes linked to autism spectrum disorders. But while research continues to advance our knowledge of autism, even improve our ability to detect it, the fact is the complex disorder almost certainly won’t be amenable to drugs or gene therapies in the way a more localized condition like Parkinson’s disease is. The hope is that we can help prevent autism with things like folic acid supplements even if we have no idea why it works.