Academics at The University of Queensland's Brain Institute and the Erasmus Medical Centre in The Netherlands analysed 4229 blood samples from pregnant women and their children who were taking part in the long-term "Generation R" study in Rotterdam.
Writing in Molecular Psychiatry, they said there was intense interest in identifying modifiable risk factors associated with autism-spectrum disorders (ASD).
“Autism-related traits, which can be assessed in a continuous fashion, share risk factors with ASD, and thus can serve as informative phenotypes in population-based cohort studies,” they added.
Although several studies have assessed vitamin D status in children with ASD, and one study has compared neonatal vitamin D status in those with ASD versus their unaffected sibling, the researchers said “no studies have examined the association between gestational vitamin D deficiency and autism or autism-related traits in general population samples.”
Maternal mid-gestation and neonatal blood tests were taken, revealing that pregnant women with low vitamin D levels at 20 weeks' gestation were more likely to have a child with autistic traits by the age of six, as defined by the Social Responsiveness Scale (SRS).
Children who were vitamin D deficient at mid-gestation were 3.8 times more likely to be screened positive than those who were vitamin D sufficient at the same point.
“The association between gestational vitamin D deficiency and a continuous measure of autism-related traits at 6 years…was determined in a large population-based cohort of mothers and their children,” the study states.
“The findings persisted (a) when we restricted the models to offspring with European ancestry, (b) when we adjusted for sample structure using genetic data, (c) when 25OHD was entered as a continuous measure in the models and (d) when we corrected for the effect of season of blood sampling.”
Lead researcher Professor John McGrath said the findings add to the body of evidence that suggests a link between low vitamin D and brain growth and neurodevelopmental disorders.
"Just as taking folate in pregnancy has reduced the incidence of spina bifida, the result of this study suggests that prenatal vitamin D supplements may reduce the incidence of autism," he said.
He said supplementation, not more sun exposure was the solution.
"We would not recommend more sun exposure, because of the increased risk of skin cancer in countries like Australia."
"Instead, it's feasible that a safe, inexpensive, and publicly accessible vitamin D supplement in at-risk groups may reduce the prevalence of this risk factor."
The study adds that future research should focus on the effect of early life vitamin D deficiency in relation to neurodevelopmental disorders.
“Alongside animal studies that aim to elucidate the biological mechanisms linking vitamin D deficiency and brain development, human studies could focus on endophenotypes to better understand the pathway from vitamin D deficiency to various neurodevelopmental disorders.”
Another recent study reported how vitamin D3 supplements improved autism sypmtoms.
Source: Molecular Psychiatry
“Gestational vitamin D deficiency and autism-related traits: the Generation R Study”
Author: J McGrath, et al.