A new study led by researchers at the University of Glasgow and to be published in the American Journal of Epidemiology has found that children conceived during the UK’s winter months have a much higher risk of being diagnosed with learning disabilities
The study (Month of conception and learning disabilities: A record-linkage study of 801,592 children), written in collaboration with researchers from the University of Cambridge, the NHS and the Scottish Government, found that 8.9% of children who had been conceived between January and March developed learning disabilities such as autism, intellectual difficulties and learning difficulties such as dyslexia. For children conceived between July and September the figure was just 7.6%.
There were no seasonal patterns for other causes of learning difficulties such as visual or hearing problems, or physical illness.
In the UK, there is insufficient sunlight in January to March for pregnant mothers to produce vitamin D, which has led the researchers to suggest that a lack of this vital vitamin may explain the trend. Vitamin D is considered essential for early brain development.
The research linked health and education data collected routinely from across Scotland in order to study more than 800,000 children who attended Scottish schools between 2006 and 2011. In 2012 guidelines were introduced that suggested that all pregnant women should take vitamin D supplements in order to prevent other conditions such as rickets. Last month Public Health England issued new advice on the use of vitamin D supplements to help maintain healthy bones, teeth and muscles.
Professor Jill Pell, Director of the Institute of Health and Wellbeing, said:
The results of this study show that if we could get rid of the seasonal variation, we could prevent 11% of cases of learning disabilities. 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.
Professor Gordon Smith, Head, Department of Obstetrics and Gynaecology, Cambridge University, 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.
The authors noted that an increased risk of flu infections early in pregnancy could also be a factor in the statistical variation, as January to March are peak months in the UK for flu.