Vitamin D halves risk of preterm delivery

By Sharon Kirkey, Canwest News Service May 1, 2010

Doctors want recommended dosage increased by 10 to 20 times

Researchers believe vitamin D has significant potential for cutting the risk of premature delivery, the leading cause of newborn deaths in Canada

All pregnant women should take 4,000 international units of vitamin D daily– 10 to 20 times the dose currently recommended by Canada’s pregnancy specialists — to lower their risk of preterm labour, preterm birth and infections, according to the first study to investigate the safety of high doses of vitamin D during pregnancy.

The study found that women in its 4,000-IU-a-day group had half the risk of premature delivery than women who took just 400 IUof vitamin D daily. Premature birth is the leading cause of newborn deaths in Canada.

And “not a single adverse event” related to vitamin D dosing was found during the study — as U.S. researchers will report Saturday 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,” says lead author Dr. Carol Wagner, a pediatric researcher at the Medical University of South Carolina.

The Society of Obstetricians and Gynaecologists of Canada currently recommends pregnant women consume 200 IU/day — and up to 400 IU in their last trimester.

But Dr. Robert Gagnon, chair of the group’s maternal fetal medicine committee, says the new study alone is reason enough to support updating those guidelines.

“The concern of giving too much vitamin D in the past was based on wrong studies,” says Gagnon, also director of maternal fetal medicine and obstetrics at McGill University and the McGill University Health Centre in Montreal.

For decades, vitamin D was thought to be a teratogen — an agent that causes birth defects –after reports from the U.K. emerged in the 1960s of babies born with heart defects, mental disabilities and elf-like facial features. Years later, it was discovered the conditions weren’t a symptom of too much vitamin D, but rather a genetic syndrome.

For their study, Wagner and colleagues randomized 494 pregnant women at 12 to 16 weeks gestation into three treatment groups: one group received 400 IUof vitamin D3 a day until delivery; another received 2,000 IU, and the third, 4,000 IU. (Vitamin D3 is better absorbed than D2.)

Higher circulating blood levels of vitamin D were associated with lower rates of preterm labour, preterm birth and infection — with the strongest effects seen in the 4,000-IU-a-day group.

It remains unclear as to how vitamin D may lower the risk of premature birth. But Gagnon said the vitamin appears to increase the amount of blood flowing to the placenta, bringing more oxygen and nutrients to the baby, and promoting healthier growth.

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Dr. Darryl Roundy

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