RESUMEN
BACKGROUND: Most extremely preterm (EP) infants are vitamin D deficient (serum 25-hydroxyvitamin D levels below 20 ng/mL), and optimal supplementation practices for EP infants remain unknown. Our objective is to assess current vitamin D supplementation practices in U.S. neonatal intensive care units (NICU) for EP infants to provide baseline information for the design of future clinical trials. METHODS: We conducted an online survey to study vitamin D intake and supplementation practices in U.S. NICUs caring for EP infants. Descriptive statistics compared responses by affiliation and level of care. RESULTS: We analyzed responses from 253 NICUs, representing the majority of academic and level IV centers. Nearly all centers (97%) provided enteral vitamin D supplementation during the NICU stay, with 400 IU/day as the most common dosage (77%). Over half (56%) used feeding volume to initiate supplementation, with 71% of centers starting after achieving at least 120 ml/kg/day. Additionally, 94% of NICUs reported prescribing a vitamin D supplementation at discharge. CONCLUSIONS: Most NICUs in the U.S. supplement EP infants with 400 IU/day of enteral vitamin D. Clinical trials of vitamin D supplementation comparing the most common regimen to earlier and higher doses are needed to identify adequate regimens for EP infants. IMPACT: Despite the prevalence of vitamin D deficiency in extremely preterm (EP) infants at birth, optimal levels and supplementation strategies remain debated. Recent studies have suggested benefits of early high-dose vitamin D supplementation (800 IU/day) for reducing complications like bronchopulmonary dysplasia, infections, and disability. There is US center variation in timing and dose of vitamin D supplementation, being the most common regimen 400 IU/d started after established feedings (≥120 ml/kg/day). These findings inform and highlight the need for clinical trials of usual vs. early, higher-dose vitamin D supplementation to advance clinical outcomes and define desirable blood levels of EP infants.