Study bolsters idea that low folic acid may increase risk in those with genetic vulnerabilities
This year brought evidence that taking prenatal vitamins during the months before and after conception may lower the risk of having a child with autism spectrum disorder (ASD)—at least if the mother or child carries certain genes that increase susceptibility to autism. The study appeared in the July issue of the journal Epidemiology.
The findings are the first to suggest a practical step women can take to reduce the risk of autism in their children. However, the results were based on interviews with fewer than 500 women and, so, need to be confirmed by the outcome of a larger study.
The study, led by Rebecca J. Schmidt, Ph.D., at University of California, Davis, is part of the larger CHARGE (Childhood Autism Risks from Genetics and the Environment) project, which continues to enroll families—both those affected by autism and those that are not. The aim of the project is to increase understanding of the causes and contributing factors that lead to ASD.
Schmidt and her colleagues based their findings on 288 children with autism and 278 children without autism, all between ages 2 to 5. After confirming autism diagnoses, they interviewed the mothers about their vitamin intake (prenatal vitamins, multivitamins, other supplements and fortified cereals) before conception, during pregnancy and while breast-feeding. The mothers who took prenatal vitamins the three months before conception and at least one month after conception were, on average, about half as likely to have a child with autism compared to mothers who did not take prenatal vitamins during this period.
Taking standard multivitamins or eating vitamin-fortified cereals did not affect autism risk. Prenatal vitamins typically contain more iron, folic acid and other B vitamins than do standard multivitamins. For years, physicians have encouraged women to take prenatal vitamins with folic acid because its use during early pregnancy reduces the risk that a baby will be born with neural tube defects, another disorder of brain development.
The researchers also analyzed DNA of the mothers and children. Women who had either one of two gene variants associated with folate regulation had double to five times the risk of having a child with autism—but only if the mother did not take prenatal vitamins around the time of conception. Children who had one of these gene variants had seven times the normal risk of developing autism if the mother did not take prenatal vitamins around conception, but just two times the normal risk if she did take them.
A deeper understanding of these gene-environment interactions may lead to improved methods for the prevention and/or treatment of autism, the researchers note. They also call for more research on the effect of other aspects of maternal nutrition and other potential environmental risk factors on crucial periods of prenatal brain development.
The ongoing CHARGE study receives funding from the National Institute of Environmental Health Sciences, the U.S. Environmental Protection Agency, UC-Davis’s MIND Institute and Autism Speaks.
Schmidt RJ, Hansen RL, Hartiala J, et al. Prenatal vitamins, one-carbon metabolism gene variants, and risk for autism. Epidemiology. July 2011;22(4):476-85.