Women who took folic acid supplements before and during pregnancy were about 40% less likely to have a baby later diagnosed with autism, a new study says.
One in 88 American children have an autism spectrum disorder, according to the Centers for Disease Control and Prevention.
In the study done in Norway, published today in the Journal of the American Medical Association, doctors asked pregnant women to fill out a questionnaire about supplement use, both before and during their pregnancies. Researchers then followed the 85,000-plus children, born from 2002 to 2008, for an average of six years.
Doctors encourage women to take folic acid before and during pregnancy because it reduces the risk of birth defects.
In this study, the critical window for folic acid consumption was four weeks before conception through the eighth week of pregnancy.
The study's results confirm findings from earlier, more preliminary studies linking folic acid and autism risk, says Craig Newschaffer, director of Drexel University's Autism Institute in Philadelphia. Other studies have found that children whose mothers took folic acid were less likely to have language delays.
Though scientists will need to confirm the results with additional studies, Newschaffer says, "It provides additional evidence that we may eventually be able to develop solid strategies to effectively prevent some forms of autism."
Folate, the natural form of folic acid, is found in lentils, spinach, black beans, peanuts, orange juice, romaine lettuce and broccoli. Most people don't get enough folic acid from food, however.
For that reason, doctors recommend all women of childbearing age take 400 micrograms of folic acid a day. In the USA, grains such as flour, rice and cereal have been fortified with folic acid since 1998. Norway does not add folic acid to foods.
Although the symptoms of autism often become clear only after a child's first birthday, this study is the latest of many suggesting that the biological changes driving autism occur either before conception or during pregnancy, says study co-author Pal Suren of the Norwegian Institute of Public Health in Oslo.
In addition to genes, factors contributing to autism include premature birth, low birth weight, prenatal exposure to certain medications or air pollution, maternal infections during pregnancy, having an older father and being born less than one year after an older sibling, studies show.
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