Vitamin D deficiency during pregnancy linked to MS risk

By Lucy Piper

Children born to mothers deficient in vitamin D during early pregnancy have an increased risk of developing multiple sclerosis (MS) as adults, researchers report.

They found that the risk of MS increased nearly twofold among children of mothers with clearly deficient serum 25-hydroxyvitamin D (25[OH]D) levels below 12.02 ng/mL, after taking into account gender, gestation age and season.

"Correcting maternal vitamin D deficiency in early pregnancy may have a beneficial effect on risk of MS in the offspring", say Kassandra Munger (Harvard T H Chan School of Public Health, Boston, Massachusetts, USA) and co-workers in JAMA Neurology.

However, they note that among the 524 women studied, most had deficient or insufficient levels of 25[OH]D below 20.03 ng/mL, according to the Institute of Medicine's guidelines, with levels above 30.05 ng/mL seen in just 11 women.

"Thus, while our results suggest that vitamin D deficiency during pregnancy increases MS risk in the offspring, our study does not provide information as to whether there is a dose-response effect with increasing levels of 25(OH)D sufficiency", the team comments.

The researchers used the Finnish Discharge Register to identify 193 individuals born to mothers in the Finnish Maternity Cohort who later developed MS, at an average age of 19.8 years, and 331 who did not. Of these, 176 MS individuals were matched to 326 controls according to region of birth in Finland, date of maternal serum sample collection and date of mother's birth and child's birth.

Blood samples were taken during the first trimester in 70% of cases and prior to week 28 in 99% of cases and 25(OH)D levels ranged from 3.50 ng/mL to 64.30 ng/mL, reflecting a deficient to sufficient level.

In the matched analysis, the risk of MS was 90% higher among the children of mothers with deficient 25(OH)D levels compared with children of mothers with sufficient vitamin D levels, the researchers report. The results obtained in the unmatched analysis were similar if slightly attenuated.

Commenting on the findings in a related editorial, Benjamin Greenberg (University of Texas Southwestern, Dallas, USA) says that autoimmunity and abnormal myelinogenesis are two theories reported to connect vitamin D deficiency and MS pathogenesis.

"Determining if autoimmune tendencies could be set into motion at the time of birth would have large implications for the field", he says. "Of greater interest would be the notion that abnormal myelinogenesis would be a risk factor for MS by creating an opportunity for antigens to be presented to the immune systems of individuals predisposed to autoimmune disease."

Greenberg concludes: "Proving this hypothesis would change our screening for individuals at risk of the disease and perhaps offer opportunities for prevention."

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