Maternal Vitamin D Levels During Pregnancy in Association With Autism Spectrum Disorders (ASD) or Intellectual Disability (ID) in Offspring; Exploring Non-linear Patterns and Demographic Sub-groups.
Gayle C Windham, Michelle Pearl, Victor Poon and 6 others
PMID 33135392WHAT IT FOUND
Mid-pregnancy vitamin D levels showed no overall association with autism or intellectual disability in offspring.
Protective effects were limited to specific subgroups, such as non-Hispanic white mothers and male children, while other groups showed no benefit or increased risk.
Key findings
01Maternal vitamin D deficiency or insufficiency in mid-pregnancy was not associated with an increased risk of autism spectrum disorder in the overall study population.
02A protective association between higher maternal vitamin D and reduced autism risk was observed only in children of non-Hispanic white mothers, but not in other racial or ethnic groups.
03The association between vitamin D and autism risk differed by child sex, showing a protective effect in males but an increased risk in females, though the female estimate was based on smaller numbers.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study population had a low prevalence of severe vitamin D deficiency, which may limit the ability to detect effects driven by severe deficiency. Findings for sex and race/ethnicity subgroups were based on smaller sample sizes, particularly for females with ASD. Vitamin D was measured only once in mid-pregnancy, so it may not reflect levels at other critical developmental windows or changes due to supplementation. Residual confounding from unmeasured factors like pre-pregnancy BMI, diet, or medications cannot be ruled out. The study was conducted in a specific geographic region (Southern California) with a distinct demographic profile, which may limit generalizability.
Declared interests
The authors declared no conflicts of interest. The study was supported by grants from the National Institute of Environmental Health Sciences and the California Department of Public Health.
The easy way to misread this
Do not interpret the protective effect in non-Hispanic white mothers or male children as evidence that vitamin D supplementation prevents autism in all populations. The primary analysis found no overall association, and subgroup findings may reflect chance or confounding rather than a causal mechanism.