Abstract
OBJECTIVE: To evaluate the effects of vitamin D supplementation on short-term respiratory outcomes in infants born at 28 weeks of gestation or less and fed human milk. STUDY DESIGN: This masked, randomized controlled trial included infants born extremely preterm and fed human milk in 2023-2024. Infants received either 800 IU/day vitamin D (intervention) or no additional vitamin D (control) for the first 14 days. Masking was maintained by adding 800 IU of vitamin D to daily feedings. The primary outcome was severity of bronchopulmonary dysplasia (BPD) at 36 weeks of postmenstrual age. Secondary outcomes included reactance and resistance (R(7-19)) measurements, obtained using impulse oscillometry at 36 weeks postmenstrual age, and metabolic bone disease (alkaline phosphatase >500 IU/L and phosphorus <5.5 mg/dL) at postnatal day 28. RESULTS: A total of 126 infants were randomized (mean birthweight: 759 ± 228 g; 52% female). The intervention increased 25-hydroxy vitamin D3 concentrations (mean difference: +29 ng/mL; P < .0001). The severity of BPD did not differ between groups (P = .60). area under the reactance curve measurements were comparable (674 ± 207 vs 694 ± 240; P = .64) and R(7-19) measurements were not significantly lower in the intervention group (23 ± 8 vs 25 ± 9; P = .18). On postnatal day 28, the lower risk of metabolic bone disease observed in the intervention group did not reach statistical significance (9% vs 20%; relative risk: 0.43; 95% CI: 0.16, 1.15; P = .08). No serious adverse events related to the intervention were reported. CONCLUSIONS: Administering 800 IU/day of vitamin D during the first 2 weeks did not reduce BPD severity but may contribute to improved bone health. TRIAL REGISTRATION: ClinicalTrials.gov: NCT05615311. https://clinicaltrials.gov/study/NCT05615311.