Monday 28 November 2016

Link between the mother’s vitamin D status and learning disabilities in the child

A link has potentially been found between a low vitamin D status in pregnant women and learning disabilities in their children. For the study, published recently in the American Journal of Epidemiology, data was used from more than 800,000 children.


It has been found that learning disabilities are more common in children who are conceived between January and March. This is the time of the year that most people at our latitude produce insufficient levels of vitamin D during exposure to sunlight. The potential result of this is that children who are born in October, November or December are more likely to have learning disabilities.


More than 800,000 children

Used for the study were the data concerning health and educational level of more than 800,000 children who were at school in Scotland between 2006 and 2011. The University of Glasgow (SCH), the National Health Service (UK) and the Scottish government worked alongside the University of Cambridge (UK) on the study.


The study revealed that 8.9 percent of children conceived between January and March have learning disabilities. Of the children conceived between July and September – and who were therefore born between April and June –7.6 percent have learning disabilities.


Autism and dyslexia

The researchers demonstrated that the difference is mainly due to more cases of autism, mental disorders and learning disabilities, such as dyslexia. In terms of other learning disabilities caused by visual or auditory disorders, no seasonal pattern was found. No link was found with the occurrence or non-occurrence of physical disorders.


First three months crucial

The researchers gained this understanding without actually measuring the vitamin D levels. Nevertheless, they believe that this is the most plausible explanation. That is because the first three months of the pregnancy are very important for brain development; when these three months are at the start of the year, the mother produces insufficient vitamin D for good brain development. According to the researchers, this had already been proven in past research.


"If the vitamin D status does indeed provide an explanation for the seasonal variation that we have seen in this study, we hope that pregnant women will take the advice that is given to take extra vitamin D early in their pregnancies. This could compensate for the variation and therefore prevent 11 percent of all learning disabilities”, say the researchers.


The researchers acknowledge that there is another possible explanation for the effect: flu infections in pregnant women are also more common between January and March and could potentially also lead to learning disabilities in the child.



Daniel F. Mackay, Gordon C. S. Smith, Sally-Ann Cooper, Rachael Wood, Albert King, David N. Clark, Jill P. Pell, Month of conception and learning disabilities: A record-linkage study of 801,592 children, American Journal of Epidemiology, September 2016.