Researchers examined the health of more than 422,500 school-age children across Scotland for the study.
UVB exposure from sunlight is linked to the production of the essential nutrient vitamin D in the body.
The study, funded by HDR UK (Health Data Research UK) and published in the journal Scientific Reports, linked sunshine hours data from the Met Office with the month children were conceived.
They found a statistically significant relationship between lower UVB exposure over the whole of pregnancy and the risk of learning disabilities.
Of the children in the study 79,616 (18.8 percent) had a learning disability, 49,770 (23.1 percent) boys and 29,846 (14.4 percent) girls.
The percentage with learning disabilities varied by month of conception, ranging from 16.5 percent among children conceived in July, to 21.0 percent for conception in February, March and April.
The relationship was specific to UVB (not UVA) suggesting the effect of sunlight was likely to be working via production of vitamin D.
During the antenatal period, the foetus undergoes rapid development and growth, making it susceptible to environmental exposures, with the potential of long-term consequences.
Maternal UVB exposure promotes the production of vitamin D, important for normal brain development of a foetus.
The researchers also found a slightly stronger relationship with low UVB exposure in the first trimester, suggesting early pregnancy may be the most vulnerable to the effects of insufficient UVB.
As a result of low levels of UVB radiation from sunlight, vitamin D deficiency is common over winter months in high latitude countries such as Scotland, with Scots twice as likely to be vitamin D deficient than people elsewhere in the UK.
Professor Jill Pell, director of the university’s institute of health and wellbeing and lead author of the study, said: “Learning disabilities can have profound life-long effects on both the affected child and their family. The importance of our study is it suggests a possible way to prevent learning disabilities in some children.
“Clinical trials are now needed to confirm whether taking vitamin D supplements during pregnancy could reduce the risk of learning disabilities.”
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