High Initial Dose of Monitored Vitamin D Supplementation in Preterm Infants (HIDVID Trial): Study Protocol for a Randomized Controlled Study.

"Conflicts of Interest The authors declare no conflicts of interest."

"This research received no external funding."

"We are implementing an unblinded, parallel-group, randomized controlled superiority trial. Parents of neonates born between 24 + 0/7 weeks and 32 + 6/7 weeks of gestation will be offered the opportunity to participate in the study within the first 24 h of the infant’s life. After providing information orally and in writing concerning the study, we will seek written consent from the parents for the neonate and mother to participate in the trial. To enhance the relevance of the research findings, we will stratify the study group by gestational age into 24–28 and 29–32 weeks of gestation subgroups. We have planned to recruit for the study for 36 months, from September 2024 to the end of 2027. The study protocol has been registered at ClinicalTrials.gov (identifier: NCT06199102). Please see for all planned patient-related activities. Institutional Review Board Statement: The study will be conducted in accordance with the Declaration of Helsinki, as well as the International Conference of Harmonization Good Clinical Practice guidelines, and has been approved by the Bioethics Committee of the Medical University of Warsaw in Warsaw, Poland (decision number KB/271/2023; 13 November 2023). Written informed consent will be obtained from parents or legal guardians before enrollment, after providing information about the methods, aims, duration, benefits, and risks of the study. Parents or legal guardians will be informed of their right to withdraw consent at any stage of the study. The study protocol is registered at ClinicalTrials.gov (Identifier: NCT06199102)."