Mutation in a high-risk gene plays large role, study finds
LOS ANGELES – Women who reported not taking prenatal vitamins immediately before and during a pregnancy were twice as likely to have a child with autism, University of California, Davis, researchers reported Wednesday. If the women also had a mutation in a high-risk gene, they were seven times as likely to have a child with the developmental disorder, the researchers reported in the online edition of the journal Epidemiology. The study is scheduled to appear in print in July.
Epidemiologist Rebecca J. Schmidt of the UC Davis MIND Institute and her colleagues studied about 700 Northern California families with 2- to 5-year-old children with autism who were participants in the Childhood Autism Risk from Genetics and the Environment study from January 2003 to December 2009. In telephone interviews, the mothers were asked whether and when they took prenatal vitamins and the type of vitamins ingested.
The team found that mothers who took the vitamins prenatally or during the first month of pregnancy were only half as likely to have a child with autism as those who didn’t. For mothers who began taking them in the second month of pregnancy, there was no effect, however. This suggests that by the time most women learn they are pregnant, beginning to take the vitamins will provide little or no benefit in terms of autism.
The researchers also found strong associations with two gene mutations that had previously been linked to autism risk. One is the variant of the methylenetetrahydrofolate reductase, or MTHFR, gene associated with less efficient metabolism of folic acid and increased blood levels of the amino acid homocysteine. The other was a variant of the catechol-O-methyltransferase, or COMT, gene, which is also linked to increased levels of homocysteine. For women who did not take vitamins and had the MTHFR variant, the risk of having an autistic child was 4.5 times normal. For those who did not take vitamins and had the COMT variant, the risk was seven times normal.