Learning disabilities are more common in children who were conceived between January and March, research in Britain has found.
A study of more than 800,000 children showed 8.9% of those conceived in the first quarter of the year had learning disabilities against 7.6% of those conceived between July and September. Glasgow University scientists believe vitamin D deficiency in mothers-to-be could explain the trend.
They found Britain does not receive enough sunlight in January, February, and March for pregnant women to produce the vitamin proven to be important for brain development.
The study, carried out in collaboration with Cambridge University, the NHS and the Scottish Government, found the seasonal differences related to autism, intellectual difficulties and learning difficulties such as dyslexia.
There were no patterns for other causes of learning difficulties like visual or hearing problems, or physical illness. The children in the research were born before 2012 guidelines advising all pregnant women to take vitamin D supplements to prevent other conditions, such as rickets.
Professor Gordon Smith, department head of obstetrics and gynaecology at Cambridge, said: “If vitamin D levels do indeed explain the seasonal fluctuations observed in this study, we would hope that widespread compliance with the advice would lead to loss of this variation, and would have a downward effect on overall rates of special educational needs.
“Although the current study did not directly measure vitamin D, it remains perhaps the most plausible explanation for the trend. Hence, these findings underline the importance of health professionals recommending vitamin D, and the importance of women complying with the treatment to optimise their chances of a healthy child,” he said.
Professor Jill Pell, director of Glasgow’s Institute of Health and Wellbeing, added: “It is important that pregnant women follow the advice to take vitamin D supplements and also that they start supplements as early in pregnancy as possible — ideally when they are trying to get pregnant.”
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