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 followed till 6 months. At enrolment, the mean (SD) serum 25(OH)D concentration were comparable in mothers in the intervention and control groups (12.90 (5.84) vs 12.84 (5.88), 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 [42.14 (17.08) vs 12.74 (6.28); P = 0.002]. The mean (SD) 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 [31.82 (10.89) vs 12.46 (5.68); 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.
Conclusions: 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.