Babies conceived in the winter between January and March are more likely to have learning difficulties because their mothers did not get enough vitamin D in pregnancy, a new study suggests.
Learning problems, such as dyslexia, reading problems and ADHD, are more prevalent in children conceived in the winter -those then born between October and December- suggesting that mothers were not getting enough of the sunshine vitamin during their first trimester.
The study of more than 800,000 children by the Universities of Glasgow and Cambridge, the NHS and the Scottish Government, found 8.9 percent of children conceived in the first quarter of the year had learning disabilities compared to 7.6 percent of those conceived between July and September.
Around 700,000 babies are born in Britain each year, which suggests an extra 2,000 children a year end up with learning difficulties.
Prof 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.
Prof 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.
Asked whether modern indoor lifestyle contributed to the rise in learning difficulties, Prof Pell added: "The suggestion is possible but reduced exposure to sunlight is likely to have occurred over decades rather than a few years and other things will also have changed over that time such as awareness, diagnosis and recording."