LOS ANGELES -- Mothers who took folic acid supplements around the time they became pregnant were less likely to have children with an autism spectrum disorder, a new study has found.
Researchers in Norway examined health records of more than 85,000 children born there between 1999 and 2009 to see whether they had some kind of autism diagnosis. They also looked at questionnaires completed by their mothers to see how much folic acid they were consuming in the month before they became pregnant and during the first eight weeks of pregnancy, a critical period of embryonic brain development.
Health officials in Norway recommend that pregnant women (and women who are trying to get pregnant) take 400 micrograms of folic acid per day.
Among the 85,176 children in the study, 270 (or 0.32 percent) received an ASD diagnosis -- 114 (0.13 percent) had autistic disorder, 56 (0.07 percent) had Asperger syndrome and 100 (0.12 percent) were diagnosed with "pervasive developmental disorder-not otherwise specified," or PDD-NOS.
These children were more likely to be born to women who did not take folic acid. In the raw analysis, mothers who skipped the supplement were more than 2.1 times more likely to have a child with autistic disorder compared with mothers who took the supplement.
But not all mothers were equally likely to take folic acid supplements. Those who did were more likely to have attended college, to be nonsmokers, to be first-time mothers and to have planned their pregnancies. The researchers also found that the popularity of folic acid supplements rose as time went on. After the researchers controlled for factors like these, they calculated that taking the supplements was associated with a 39 percent lower risk of having a child with autistic disorder.
The raw numbers also showed that women who took extra folic acid were less likely to have kids with Asperger syndrome or PDD-NOS, but when other factors were taken into account, the association was no longer statistically significant and could have been due to chance, the researchers found.
The results were published in Wednesday's edition of the Journal of the American Medical Association.
The study also looked at folic acid use later in pregnancy but found no correlation between that and the chances of a child developing an autism spectrum disorder. Nor did they find any link between fish oil supplements and risk of ASDs.
It's unclear how these findings apply to mothers and children in the United States. Autism spectrum disorders are diagnosed much more frequently in the U.S. than in Norway.