But the supplement has no effect if it is started more than 8 weeks into the pregnancy.
In a new study, women who took vitamin B9 supplement (folic acid) from four weeks before conception to eight weeks into pregnancy had a 40 percent lower risk of giving birth to children with childhood autism (classic autism).
“It appears that the crucial time interval is from four weeks before conception to eight weeks into pregnancy,” states Pål Surén, MD and doctoral fellow at the Norwegian Institute of Public Health.
The study is based on the Norwegian Mother and Child Cohort Study (MoBa) and the Norway Autism Birth Cohort Study (ABC). It covered a total of 85 176 children born in the period 2002–2008.
Folic acid is a B vitamin that is essential for the construction and repair of DNA molecules, which control all body cells. Folate is the naturally occurring form of folic acid found in food and in the body.
Most pregnant women need folic acid supplements to reach the daily recommended levels. The Norwegian Directorate of Health recommends that women who are planning to become pregnant start to take folic acid supplements one month before conception and during the first three months of pregnancy.
The results of the study of the correlation between intake of folic acid supplements and childhood autism indicate that the lower risk is only associated with this specific supplement and not with the consumption of food or other supplements.
“Thus, the findings show that a measure already used here in Norway, one which is simple, inexpensive and without any known side effects among pregnant women, can prevent autism. Previous studies we have carried out have shown that folic acid may have a similar effect on other developmental disorders as well,” says Surén.
The Directorate of Health’s recommendations regarding pre-natal folic acid supplements are based on research that shows that the vitamin protects the foetus against spina bifida and other neural tube defects.
The researchers have also found a correlation between folic acid supplements and the reduced risk of severe language delay by the age of three. Such language problems are common in connection with autism but may also occur with many other conditions.
“It will be a tremendous breakthrough if it turns out that folic acid also prevents other developmental disorders,” Surén believes.
Surén and his colleagues will conduct new analyses when the children involved in the study are older, among other things to examine whether there is any correlation between folic acid and a reduced risk of other developmental disorders such as ADHD and cerebral palsy. They will also carry out genetics studies.
“We know that there is a genetic component to the body’s ability to use folate, so it is possible that some mothers are more prone to folic acid deficiency than others,” Surén adds.
The study was recently published in the Journal of the American Medical Association (JAMA).
The Norwegian Mother and Child Cohort Study (MoBa)
The mothers participating in the MoBa Study have provided detailed information about their eating habits and use of dietary supplements early in their pregnancy. Children with autism diagnoses involved in the study were identified using questionnaires, through referrals from parents and the National Health Service and through the Norwegian Patient Registry.
The Research Council of Norway’s national initiative on neuroscientific research (NevroNor) provided funding for the use of the data from the Norwegian Patient Registry (NPR). The research activity carried out in connection with the ABC Study was also primarily funded under various programmes at the Research Council.