Clinical Implications and Preventive Strategies for Neonatal and Infant Hypovitaminosis D: Analysis and Comparison of Current Evidence

Background: Vitamin D is essential for neonatal health, with maternal vitamin D status crucial in fetal development and neonatal outcomes. During pregnancy, vitamin D is transferred to the fetus via the placenta, forming an initial reserve. Postnatally, neonates rely on maternal levels and supplementation due to limited sunlight exposure and immature skin synthesis. Objectives: This review evaluates neonatal vitamin D deficiency’s causes and clinical consequences, emphasizing its impact on newborn and infant health. Results: Maternal vitamin D levels strongly correlate with neonatal 25(OH)D concentrations, influencing birth weight, bone development, and overall health. Supplementation during pregnancy reduces the risk of severe deficiencies and rickets, particularly in exclusively breastfed infants who require daily supplementation of 400 IU. Formula-fed infants typically meet requirements through fortified formulas. Preterm infants are at a higher risk of complications like osteopenia and rickets, with mixed evidence on the effectiveness of higher supplementation doses. Vitamin D is critical in skeletal development, immune function, and protection against respiratory infections such as bronchiolitis and pneumonia. Deficiency is associated with respiratory distress syndrome (RDS), atopic dermatitis, and impaired bone mineralization due to reduced placental calcium transport. Conclusions: Vitamin D deficiency during pregnancy and infancy has significant clinical implications, including impaired skeletal and immune development. Maternal and neonatal supplementations are critical to prevent deficiencies, particularly in high-risk groups such as preterm and breastfed infants. Targeted strategies are essential to improve neonatal health outcomes and prevent complications.