Children whose mothers took folic acid supplements early in their pregnancies were less likely to develop autism, even when the pregnant moms were exposed to pesticides linked to the neurodevelopmental disorder, a new study in Environmental Health Perspectives found.
Mothers who were exposed to household or agricultural pesticides just before and during their pregnancies but who took high-dose folic acid cut in half the risk of their children developing autism when compared to women who received low doses of the vitamin, lead author Rebecca Schmidt said in a phone interview.
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"If there's a chance you might get pregnant, . . . take your folic acid and try to avoid unnecessary pesticides," said Schmidt, an epidemiologist and professor at the Medical Investigations of Neurodevelopment Disorders (MIND) Institute at the University of California, Davis.
The research confirmed previous studies connecting maternal pesticide exposure to autism spectrum disorder (ASD), a developmental disability marked by social, communication and behavioral challenges.
Children prenatally exposed to pesticides were less likely to be diagnosed with autism if their mothers took a high dose of folic acid.
But the report in Environmental Health Perspectives breaks new ground by finding that children prenatally exposed to pesticides were less likely to be diagnosed with autism if their mothers took a high dose of folic acid.
The findings led investigators to conclude that folic acid might reduce, though not eliminate, an increased risk of autism associated with maternal pesticide exposure.
Folic acid, or vitamin B-9, is contained in green leafy vegetables and fortified cereal.
The U.S. Preventive Services Task Force and other health groups already urge women with any chance of becoming pregnant to take daily folic acid supplements because B-9 deficiency has long been tied to brain and spinal cord birth defects.
The new findings, in addition to underscoring the importance of folic acid, highlight the role environmental pollutants appear to play in the development of autism, said Joseph Braun, an epidemiologist at the Brown School of Public Health in Providence, Rhode Island, who was not involved with the study.
There has really not been as much attention paid to environmental risk factors for autism as there has been for genetic risk factors.
"This is another piece of the puzzle for environmental risk factors for autism," he said in a phone interview. "There has really not been as much attention paid to environmental risk factors for autism as there has been for genetic risk factors."
An estimated one of every 68 children in the U.S. was diagnosed with an autism spectrum disorder in 2012, according to the U.S. Centers for Disease Control and Prevention. Since the 1990s, rates of autism have spiked across the nation. Boys are 4.5 times more likely to be diagnosed with ASD than girls.
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Study participants included 296 children diagnosed with autism and 220 who developed typically. All were between two and five years old and born in California from 2000 until 2007.
Researchers interviewed the children's mothers about their folic acid intake as well as their exposure during pregnancy to household pesticides, including pet flea and tick products, professional pest control or extermination, and indoor and outdoor sprays and chemicals intended to kill insects. Investigators also linked data from state pesticide-use reports with mothers' addresses to determine exposure to agricultural sprays.
Women with below-average folic acid intake and exposure to any indoor pesticides had 2.5 times the risk of having a child with autism compared to unexposed mothers who took at least 800 micrograms of folic acid, the amount in prenatal vitamins.
Mothers who were exposed regularly to pesticides for three months before and after conception were at the highest risk of having children who developed ASD, Schmidt said.
While folic acid reduced the risk of a child developing autism, it did not eliminate it.
While folic acid reduced the risk of a child developing autism, it did not eliminate it, the study found.
The study relied on mothers' memories about their household pesticide exposure, a limitation of the research, Schmidt said. But researchers were able to draw similar conclusions from California pesticide-use data as they did from self-reported pesticide usage, strengthening the findings, Braun noted.
The study shows promise for nutritional supplements mitigating the damage from prenatal pollutants, he and Schmidt said.
"Maybe this is a way to attenuate effects of environmental pollutants and contaminants that we don't really have a lot of control over," Schmidt said.
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