Pregnant women who have higher levels of vitamin D in their blood may have a lower risk of developing multiple sclerosis (MS) than women with lower levels, while their babies may not see the same protective effect, according to a study published in the November 20, 2012, online issue of Neurology®, the medical journal of the American Academy of Neurology.

"In our study, pregnant women and women in general had a lower risk for MS with higher levels of the vitamin, as expected. However, a mother's levels of vitamin D during early pregnancy did not have an effect on MS risk for her baby," said study author Jonatan Salzer, MD, with Umeå University Hospital in Sweden.

For the study, scientists reviewed information about 291,500 blood samples from 164,000 people collected since 1975 in the northern half of Sweden. Of those, 192 people developed MS an average of nine years after their blood sample was drawn, and there were 37 blood samples drawn during pregnancy from mothers whose children went on to develop MS later in life.

The research found that women who had high levels of vitamin D in their blood had a 61 percent lower risk of developing MS, compared to those who had low levels of vitamin D in their blood. Overall, few people had high levels of vitamin D. Only seven of the 192 people who developed MS, or four percent, had high vitamin D levels, compared to 30 of 384 controls without the disease, or eight percent.

No association was found between the mother's vitamin D level and whether her child would later develop MS.

"Since we found no protective effect on the baby for women with higher levels of vitamin D in early pregnancy, our study suggests the protective effect may start in later pregnancy and beyond," said Salzer. "Another interesting finding in our study was that the vitamin D levels became gradually lower with time from 1975 and onward. It is possible that this decline in vitamin D status is linked to the increasing numbers of MS cases seen worldwide."