Researchers believe medical professionals should be advising pregnant women to take vitamin D supplements to reduce the chances of having a baby which later develops multiple sclerosis.
Authors of a study examining people living in locations more than 52 degrees away from the equator say there is strong evidence that expectant mothers should take vitamin D supplements in places where levels of sunlight are low from October to March.
The report, which has been published online in the Journal of Neurology, Neurosurgery and Psychiatry, claims people born in April are most at risk of developing MS, while those with birthdays in October are least likely to be diagnosed with the condition.
Academics looked at information which has already been published on almost 152,000 patients with MS and compared it to the numbers of people expected to develop the disease to see if the country the person lived in affected the likelihood of getting MS.
The authors claim that people living in countries at latitudes more than 52 degrees from the equator are not exposed to enough ultraviolet light during the winter months to make the amount of vitamin D needed during the winter.
The report found people with an April birthday were 5% more likely to be diagnosed with MS during their lifetime than those born in other months. While being an October or November baby reduced their risk by between 5% and 7%.
The authors then carried out a further “conservative analysis” in which they excluded studies in which the data overlapped but still concluded that those born in April and May were most at risk of developing MS while those in October and November were the least likely to be diagnosed with the disease.
The authors said that their findings strengthened the case for taking a vitamin D supplement throughout pregnancy to potentially cut the number of cases of MS.