Effect of Antenatal Oral Vitamin D Supplementation on Serum 25(OH)D Concentration in Exclusively Breastfed Infants at 6 Months of age - A Randomized Double-Blind Placebo-Controlled Trial

Objective: To compare the proportion of exclusively breastfed (EBF) infants having severe vitamin D deficiency (25(OH)D concentration <11 ng/mL) at 6 months of age when mothers were supplemented with 300,000 IU vitamin D3 or placebo during the third trimester of pregnancy. Methods: In this randomized double-blind placebo-controlled trial, we recruited 100 pregnant women (who were willing to exclusively breastfeed their babies for 6 months) at 30-32 weeks gestation and the infants born to them. Pregnant women were randomized to receive either oral vitamin D3 60,000 IU or placebo, given weekly for 5 weeks during the third trimester. Serum 25(OH)D, calcium, phosphorus and alkaline phosphatase concentration were measured in all participants at recruitment, in the cord blood at delivery, and in infants at 6 months of age. The proportion of infants developing severe vitamin D deficiency and rickets at 6 months was assessed. Results: A total 72 mother-infant dyads were followed-up till 6 months. At enrollment, the mean (SD) serum 25(OH)D concentration (ng/mL) were comparable in mothers in the intervention and control groups [12.9 (5.8) vs 12.8 (5.9), P = 0.96]. The mean (SD) 25(OH)D concentration (ng/mL) in the cord blood was significantly higher in the intervention group compared to the control group [42.1 (17.1) vs 12.7 (6.3); P = 0.002]. Serum 25(OH)D levels (ng/mL) in the infants at 6 months age were higher in the intervention group compared to the control group [31.8 (10.9) vs 12.5 (5.7); P < 0.001]. No infant in the intervention group had severe vitamin D deficiency at 6 months age compared to 54.3% infants in the control group (P < 0.001). No infant in the intervention group developed rickets. Conclusion: Oral supplementation of vitamin D3 to pregnant women in the third trimester prevents severe hypovitaminosis D in the EBF infants at 6 months of age.