Folic acid has been recommended to pregnant women for years, usually as a way to prevent birth defects such as spina bifida.
But a new study published today in the Journal of the American Medical Association found it may also prevent autism.
The study comes at a time when pregnant women are increasingly worried about how their actions will affect their growing fetuses — from eating certain foods to getting vaccines to dying their hair.
“Many women have significant concerns, anxiety and stress during pregnancy about the things that they eat, consume or come into contact with in an environmental sense,” said Dr. Jennifer Ashton, a senior medical contributor to ABC News.
The JAMA study, which used data from the Norwegian Mother and Child Cohort Study, found that mothers who took folic acid four weeks before and eight weeks after pregnancy had a 40 percent reduced risk of giving birth to a child with autism. While the researchers found an association between folic acid deficiency and autism, that does not mean that folic acid taken during pregnancy would result in fewer autism cases.
“We know that folic acid deficiency leads to defects in the development of the nervous system,” said Dr. Ari Brown, a pediatrician in Texas, who was not involved in the JAMA study, referring to spina bifida. “So it would not be surprising that a deficiency might also affect brain development in other ways.”
The Norwegian Mother and Child Cohort Study followed more than 85,000 babies born between 2002 and 2008, and their parents. About 270 babies whose parents participated in the study were born with a developmental disorder on the autism spectrum.
Mothers reported whether they were taking folic acid before and during early pregnancy before they found out whether their children had autism, which eliminated some potential bias, said molecular epidemiologist Rebecca Schmidt, a professor at the University of California, Davis School of Medicine. In 2011, Schmidt was one of the first scientists to publish a study that found that autism arises because of both genetic and external factors, including women’s prenatal vitamin intake before conception.
“Given the replication of findings showing reduced risk of autism associated with folic acid supplements taken near conception, more research is needed to investigate whether this association is causal,” she said. “Interestingly, both studies reported … a nearly 40 percent reduction in risk for autism.”