A new study has linked folic acid supplements in pregnancy with a 39% lower risk of autistic disorder in the offspring but experts have urged caution in interpreting the results.
Doctors have long recommended that women aiming to fall pregnant take folic acid supplements before they conceive and during pregnancy because they lower the risk of neural tube defects like spina bifida.
However, a new Norwegian study of 85,176 children published in the journal JAMA today found that maternal consumption of folic acid from four weeks before to eight weeks after conception was linked with a lower risk of the child developing autistic disorder.
Autism spectrum disorders include autistic disorder, Asperger syndrome and pervasive developmental disorder-not otherwise specified (PDD-NOS).
The researchers analysed data from the Norwegian Mother and Child Cohort Study, tracking children born between 2002 and 2008.
Results were adjusted for maternal education level, year of birth and the number of live children the mother had delivered.
The authors found 0.1% of the children whose mothers took folic acid developed autistic disorder, compared to 0.21% of the children whose mothers did not take folic acid in pregnancy.
In other words, maternal folic acid supplementation was linked with 39% lower odds of autistic disorder in the offspring.
“No association was found with Asperger syndrome or PDD-NOS, but power was limited,” the researchers said in their paper.
“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.”
Co-author of the study, Dr Pål Surén from the Norwegian Institute of Public Health, said the women studied in this project were recruited from all 19 counties of Norway, and all categories of education and income levels were well represented.
“It is true that socially disadvantaged women were underrepresented, but the vast majority of Norwegian women are not socially disadvantaged,” he said.
“Furthermore, we do not have reason to believe that the association between folic acid use and autism risk is considerably influenced by selection bias in the cohort. When we compared the MoBa population to the general Norwegian population, we obtained similar estimates of relative risk,” he said.
“And if we were to speculate about the potential effects of folic acid in socially disadvantaged women, I would think it would be greater, given that they are likely to have poorer diets, with a lower intake of dietary folate.”
Andrew Whitehouse an autism expert at the Telethon Institute for Child Health Research, University of Western Australia, said the study was well-conducted and showed that “mothers who took folic acid prior to conception and during the early stages of pregnancy had a reduced likelihood of having a child with autism.”
“The findings only indicated a reduced-risk for Autistic Disorder, and not for the less severe forms of autism such as Asperger’s Disorder or Pervasive Developmental Disorder- Not Otherwise Specified,” said Dr Whitehouse, who was not involved in the study.
“The main word of caution is that the researchers have only identified an association and they cannot determine whether folic acid causes a reduced risk of autism spectrum disorder.”
A second, very important finding, is that folic acid supplementation did not lead to an increased risk for autism spectrum disorder diagnoses, he said.
“We know that folic acid is important for the reduction of neural-tube defects, and Australia has been fortifying flour since September 2009,” said Dr Whitehouse.
“These findings indicate that this fortification doesn’t lead to other un-forecast problems, such as increasing risk for autism spectrum disorder. This is very comforting.”