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MS risk affected by 'birth month effect'

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The strength of a newborn’s immune systems and their vitamin D levels are strongly influenced by the month of the year they were born in, new research has confirmed.

The findings may help to explain why the risk of developing multiple sclerosis (MS) is dependent on a child’s birth month, according to a study published in the journal JAMA Neurology.

The study by scientists at Queen Mary, University of London and the University of Oxford also called for further research into the possible beneficial effects of vitamin D supplementation during pregnancy.

Low doses of vitamin D are linked to a variety of harmful outcomes during pregnancy, past studies have shown.

A vitamin D deficiency during pregnancy can cause gestational diabetes and preeclampsia, as well as low birth weight in newborns.

A separate study published in the journal Neurology last year found that elevated levels of vitamin D during pregnancy could later prevent multiple sclerosis in the mothers.

Population studies have indicated that the month you are born can impact your risk of developing MS.

The so-called “birth month effect” is particularly pronounced in England, with those born in May most likely to contract MS and those born in November showing a decreased risk of the disease.

The effect has been understood as evidence of a prenatal role for vitamin D in the risk of MS.

The study looked at samples of cord blood from 50 babies born in November and 50 born in May between 2009 and 2010 in London.

The May babies’ vitamin D levels were around 20% lower and had almost twice as many autoreactive T-cells compared with the November sample.

Dr Sreeram Ramagopalan, co-author and neuroscience lecturer at Barts and The London School of Medicine and Dentistry, said: “By showing that month of birth has a measurable impact on in utero immune system development, this study provides a potential biological explanation for the widely observed ‘month of birth’ effect in MS.

“Higher levels of autoreactive T-cells, which have the ability to turn on the body, could explain why babies born in May are at a higher risk of developing MS.”


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