Mothers who took 4,000 IU of vitamin D daily cut their risk of premature delivery by half, in a study conducted by researchers from the Medical University of South Carolina and presented at the annual meeting of the Pediatric Academic Societies in Vancouver.
“We never imagined it would have as far-reaching effects as what we have seen,” lead author Carol Wagner said. “The message is that all pregnant women should be supplementing with 4,000 IU per day of vitamin D.”
Researchers assigned 494 women between their 12th and 16th weeks of pregnancy to take either 400 IU, 2,000 IU or 4,000 IU of vitamin D per day. They found that the more vitamin D a pregnant woman took, the higher the levels of the vitamin in her blood and in that of the child at birth.
Higher levels of vitamin D were significantly associated with a lower risk of infection, preterm labor and preterm birth.
Premature birth is the foremost cause of newborn death in Canada.
Vitamin D has long been known to play an important role in the development and maintenance of healthy teeth and bones, and newer research has implicated it in maintaining a healthy immune system and preventing infection, cancer, heart disease and autoimmune disorders. Yet for a long time, researchers falsely believed that the vitamin could cause birth defects.
Later, researchers discovered that the defects initially attributed to vitamin D were caused by a genetic defect that affected the vitamin’s metabolism in the body.
“For 30-plus years it was dogma that [vitamin D in pregnancy] was dangerous, that you didn’t need very much and what you did need you could get from just casual sunlight exposure,” Wagner said. “What we know now, from a decade of very intensive research, is that that’s not the case.”
Wagner cautioned that even though the study took place in South Carolina, 85 percent of participants had insufficient vitamin D levels when the study began.
“This is even more important for Canadians,” Wagner said. “You’re at a much higher latitude. The best that you can have is probably six months of sunlight exposure, at your lowest latitude, where you can actually make vitamin D.”