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Vitamin D Cuts Risks of Pregnancy

Jacob Schor, ND, FABNO

May 3, 2010

Women who take vitamin D supplements during pregnancy have reduced risk of complications including premature birth according to a recent randomized trial.

Women taking high daily doses of vitamin D had half the risk of problems as those in the control group.  [relative risk 0.50, 95% confidence interval: 0.27 - 0.95, P=0.03]

The bottom line is that pregnant women should take 4,000 IU a day, at least according to this study by Carol Wagner, MD, of the Medical University of South Carolina in Charleston.

According to Wagner,  this dose is not only safe, but prevents a range of complications associated with pregnancy.

Obviously it is higher than the RDA for vitamin D that ranges from 200 IU a day for children to 600  IU for adults over 70.


Wagner and her colleagues enrolled 494 pregnant women in a randomized trial of three daily doses of the vitamin -- 400, 2,000, and 4,000 IU a day until delivery. The goal was to see if the higher doses were more effective at reducing complications.

350 women continued in the study until delivery, including 98 African-American women, 137 Hispanics, and 115 Caucasian women.

Of those who continued, 111 were taking 400 IU (the control group), 122 took 2,000, and 117 took 4,000.

The researchers report several effects:

1.  Average serum levels of vitamin D differed between all the groups before and after delivery.

2.  As vitamin D levels increased so did calcitriol, the active form of vitamin D.  Calcitriol levels peaked when vitamin D reached 40 ng/ml.

3. The rates of pre-term labor, pre-term birth, and infection were lowest in the group taking 4,000 IU of vitamin D per day..

4.  In women who ended up having problems during pregnancy the average blood level of vitamin D was 33.4 ng/ml.  In the women who didn’t have complications, the average level was 39 ng/ml.

The babies born of the women in the control group who only took 400 iu/day had average vitamin D levels of 18.2 ng/ml.    the babies born of the women taking 2,000 IU per day had average vitamin D levels of 22.8 ng/ml and those born of women taking 4,000 IU averaged 26.5 ng/ml.  Most researchers consider 30 ng/ml. to be the low end of the acceptable range for vitamin D levels.



Wagner CL et al. "Vitamin D supplementation during Pregnancy Part 2 NICHD/CTSA Randomized Clinical Trial (RCT): Outcomes" PAS 2010; Abstract 1665.6.

Wagner CL et al. "Vitamin D supplementation during Pregnancy Part I NICHD/CTSA Randomized Clinical Trial (RCT): Safety Considerations" PAS 2010; Abstract 2630.7.

This article was edited down from the original article written by Michael Smith that appeared on Medscape, May 1 2010.