Study Title:

Vitamin D Needs During Pregnancy

Study Abstract

The need, safety and effectiveness of vitamin D supplementation during pregnancy remain controversial.

In this randomized controlled trial, women with a singleton pregnancy at 12-16 weeks' gestation received 400, 2000 or 4000 IU vitamin D3/day until delivery. The primary outcome was maternal/neonatal circulating 25(OH)D at delivery, with secondary outcomes 25(OH)D ≥80 nmol/L achieved and 25(OH)D concentration required to achieve maximal 1,25(OH)2D production.

Of the 494 women enrolled, 350 women continued until delivery: Mean 25(OH)D by group at delivery and 1-month before delivery were significantly different (p < 0.0001), and percent who achieved sufficiency was significantly different by group, greatest in 4000 IU group (p < 0.0001). The relative risk (RR) for achieving ≥80 nmol/L within one month of delivery was significantly different between 2000 vs. 400 IU (RR 1.52 [CI 1.24-1.86]), 4000 vs. 400 (RR 1.60 [CI 1.32-1.95]), but not between 4000 vs. 2000 (RR 1.06 [CI 0.93-1.19]). Circulating 25(OH)D had a direct influence on circulating 1,25(OH)2D concentrations throughout pregnancy (p < 0.0001) with maximal production of 1,25(OH)2D in all strata in the 4000 IU group. There were no differences between groups on any safety measure. Not a single adverse event was attributed to vitamin D supplementation or circulating 25(OH)D levels.

Vitamin D supplementation of 4,000 IU/day for pregnant women was safe and most effective in achieving sufficiency in all women and their neonates regardless of race while the current estimated average requirement was comparatively ineffective at achieving adequate circulating 25(OH)D, especially in African Americans. © 2011 American Society for Bone and Mineral Research

From press release:

Use of vitamin D supplements during pregnancy has long been a matter of concern but now researchers writing in the Journal of Bone and Mineral Research report that even a high supplementation amount in healthy pregnant women was safe and effective in raising circulating vitamin D to a level thought by some to be optimal. The study also found no adverse effects of vitamin D supplementation, even at the highest amount, in women or their newborns.

The research team, led by Dr. Bruce Hollis from the Medical University of South Carolina in Charleston, used a randomized controlled trial with healthy expectant mothers to discover how varying dosages of daily supplements could safely sustain a circulating vitamin D level of at least 32 nanograms per milliliter.

"Vitamin D supplementation during pregnancy remains controversial largely due to severe misconceptions about the potential harm it may cause to the fetus," said Dr Hollis. "Surprisingly the scientific debate has made little progress since Dr. Gilbert Forbes made a recommendation of 200 IU (international units) per day in 1963, which was based on a hunch."

While the threat of vitamin D during pregnancy has remained little known, it has been established that the vitamin plays a role in homeostasis, the body's internal regulation, during pregnancy and that a deficiency can effect immune, pancreatic and cardiovascular systems.

Dr Hollis' team monitored the pregnancies of 350 women, from a variety of ethnic and socio-economic backgrounds, who were all between 12 and 16 weeks into gestation. The women were randomly assigned to one of three groups. One group received 400 IU of vitamin D per day, the second group received 2,000 IU per day and the third received 4,000 IU daily.

The team found that women who received the highest level of supplementation (4,000 IU per day) were more likely to achieve and sustain the desired level of circulating levels of vitamin D throughout their pregnancy. Moreover, the researchers found that pregnant women who received lower levels of vitamin D supplementation did not attain the threshold circulating level of the vitamin.

"In our study subjects, a daily dosage of up to 4,000 IU of vitamin D was required to sustain normal metabolism in pregnant women," concluded Dr Hollis. "Furthermore, following decades of speculation into its safety our research has demonstrated vitamin D supplementation to be both safe and effective."

Study Information

B. Hollis, D. Johnson , T. Hulsey, M. Ebeling, L. Wagner
Vitamin D Supplementation during Pregnancy: Double Blind, Randomized Clinical Trial of Safety and Effectivness.
Journal of Bone and Mineral Research
2011 June
Medical University of South Carolina in Charleston

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