Newborn babies’ immune systems and vitamin D levels differ – depending on which month of the year they were born, Medical News Today reported.

The study, published in the journal JAMA Neurology, helps explain why a person’s risk of developing the neurological condition multiple sclerosis (MS) is impacted by their birth month.

Multiple sclerosis is a neurological condition in which the body’s own immune system harms the central nervous system. It obstructs the passing of messages between the brain and other areas of the body and can result in issues with memory, hearing, muscle control and vision.

Several studies have indicated that the month in which you were born can influence your risk of developing MS – a phenomenon known as the “birth month effect.”  The risk of MS appears to be highest for people born in May, and lower in those born in November, particularly for people living in England.

The study also identifies the need for more research into the potential advantages of vitamin D supplementation during pregnancy, Medical News Today said. Previous studies have suggested that low levels of vitamin D during pregnancy can result in gestational diabetes, preeclampsia and low birth weight in newborns.

And another study, published in the journal Neurology last year, indicated that higher levels of vitamin D during pregnancy could later prevent multiple sclerosis in mothers.

For the JAMA study, blood samples were taken from the umbilical cords of 50 babies born in November and 50 babies born in May. Researchers looked at levels of vitamin D and levels of autoreactive T-cells in the babies’ blood.

T-cells are the white blood cells that help the body’s immune system attack infectious agents like viruses. However, when T-cells are autoreactive, they attack the body’s healthy cells, causing autoimmune diseases.

The blood tests indicated that babies born in May had significantly lower levels of vitamin D and higher levels of autoreactive T-cells, compared to babies born in November, Medical News Today said.

Study co-author Dr. Sreeram Ramagopalan, a lecturer in neuroscience at Barts and The London School of Medicine and Dentistry, part of Queen Mary, concluded:

"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.

“The correlation with vitamin D suggests this could be the driver of this effect,” Ramagopalan added. “There is a need for long-term studies to assess the effect of vitamin D supplementation in pregnant women and the subsequent impact on immune system development and risk of MS and other autoimmune diseases."

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