Jenni Laidman
December 16, 2013
Vitamin D supplements for pregnant women and their newborns increased the proportion of infants with serum vitamin D levels recommended by the Institute of Medicine (IOM), according to a double-blind, placebo-controlled trial published online December 16 in Pediatrics.
Cameron C. Grant, MBChB, PhD, associate professor, pediatrics: child and youth health, University of Auckland School of Medicine, New Zealand, and colleagues randomly assigned 260 pregnant women into 1 of 3 cohorts to determine how much vitamin D supplementation was required to achieve serum 25-hydroxyvitamin D [25(OH)D] concentrations of 20 ng/mL or more in infancy, as recommended by the IOM in 2011. Recruitment was evenly distributed across seasons, and the sample included a variety of skin pigmentations, the authors state.
In the trial, a group of 87 women received a placebo during pregnancy, and their babies also received a placebo through 6 months of age. A second group of 87 women received 1000 IU vitamin D3, and their infants received 400 IU through age 6 months. The third group of 86 women received 2000 IU vitamin D3, and their infants received 800 IU through age 6 months. About half of the women in each group started with serum 25 (OH)D levels of 20 ng/mL or more: 54% in the placebo group, 64% in the 1000-IU group, and 55% in the 2000-IU group.
New Zealand is one of many countries that does not mandate vitamin D fortification of food, nor does it routinely recommend vitamin D supplementation. The United States and Canada both mandate the fortification of infant formula with vitamin D, at 40 to 100 IU/100 kcal in the United States and 40 to 80 IU/100 kcal in Canada. Canada mandates milk fortification at 35 to 40 IU/100 mL, and most milk in the United States is fortified voluntarily at 100 IU/cup.
At 36 weeks’ gestation, the proportion of women in the trial with serum 25(OH)D levels of 20 ng/mL or higher was greater in both groups receiving supplements, with 91% of the women in the lower-supplement group and 89% of women in the higher-supplement group at 20 ng/mL or higher compared with 50% for the placebo group (P < .001).
The results were similar when 25(OH)D was measured in cord blood and in the infants at age 2 months and 4 months, but at 6 months, the difference was significant only in the higher-dose group.
In cord blood, 22% of the placebo group reached a level of 20 ng/mL or higher, as did 72% of the 1000-IU group and 71% of the 2000-IU group (P < .001). At age 2 months, 50% of the placebo group reached a level of 20 ng/mL or higher, as did 82% of the lower-dose group and 92% of the higher-dose group (P < .001). At age 4 months, 66% of the placebo group reached the recommended vitamin D level, as did 87% of the lower-dose group and 87% of the higher vitamin D supplement group (P = .004).
At age 6 months, 74% of the infants taking a placebo reached serum 25 (OH)D levels of 20 ng/mL or higher, as did 82% of infants given 400 IU daily and 89% of the infants given 800 IU daily. The difference was significant only between the highest-dose group and the placebo group (P = .03).
No study participant incurred hypercalcemia, not even 5 infants who at 2 months had serum 25(OH)D concentrations of 100 ng/mL or higher.
The authors conclude that achieving recommended levels of vitamin D requires supplementation for both the mother and the infant. “For serum 25(OH)D concentration to be maintained throughout infancy, it is likely to also require dose adjustment to meet the demands created by rapid growth during infancy,” they write.
The pregnancy and infancy vitamin study was funded by the Health Research Council of New Zealand. One coauthor is supported by Cure Kids. Study medicine was prepared by the Ddrops Company. The authors have disclosed no relevant financial relationships.
Pediatrics. Published online December 16, 2013.