Abstract: OBJECTIVE: To determine the vitamin D dose necessary to achieve serum 25-hydroxyvitamin D (25(OH)D) concentration ≥20 ng/mL during infancy. METHODS: A randomized, double-blind, placebo-controlled trial in New Zealand. Pregnant mothers, from 27 weeks’ gestation to birth, and then their infants, from birth to age 6 months, were randomly assigned to 1 of 3 mother/infant groups: placebo/placebo, vitamin D 3 1000/400 IU, or vitamin D 3 2000/800 IU. Serum 25(OH)D and calcium concentrations were measured at enrollment, 36 weeks’ gestation, in cord blood, and in infants at 2, 4, and 6 months of age. RESULTS: Two-hundred-and-sixty pregnant women were randomized. At enrollment, the proportions with serum 25(OH)D ≥20 ng/mL for placebo, lower-dose, and higher-dose groups were 54%, 64%, and 55%, respectively. The proportion with 25(OH)D ≥20 ng/mL was larger in both intervention groups at 36 weeks’ gestation (50%, 91%, 89%, P P P P = .004), but only in the higher-dose group at age 6 months (74%, 82%, 89%, P = .07; higher dose versus placebo P = .03, lower dose versus placebo P = .21). CONCLUSIONS: Daily vitamin D supplementation during pregnancy and then infancy with 1000/400 IU or 2000/800 IU increases the proportion of infants with 25(OH)D ≥20 ng/mL, with the higher dose sustaining this increase for longer.
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