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Bidirectional changes in serum 25-hydroxyvitamin D in newborns during the first four days of life: A longitudinal
Kazushige Ikeda1, Kaori Hara-Isono2, Kazumi Morisawa2
1Division of Maternal and Child Health, Department of Pediatrics, Saitama City Hospital, Saitama, Japan.
Insights
Neonatal vitamin D levels show dynamic changes in the first four days of life. Infant vitamin D status (25(OH)D) influences whether levels rise or fall, indicating physiological regulation.
Area of Science:
- Neonatal physiology
- Nutritional biochemistry
- Pediatric endocrinology
Background:
- Limited understanding of short-term vitamin D dynamics in newborns.
- Most studies use single-point measurements of 25-hydroxyvitamin D (25(OH)D).
- Unique Japanese hospital setting with minimal vitamin D intake and sun exposure.
Purpose of the Study:
- To examine short-term changes in serum 25(OH)D from birth to day 4.
- To determine how baseline vitamin D status influences these early postnatal changes.
Main Methods:
- Analysis of paired cord blood and day 4 serum 25(OH)D in 40 infants.
- Chemiluminescence immunoassay for 25(OH)D measurement.
- Linear regression to assess the association between cord blood 25(OH)D and change in 25(OH)D (Δ25(OH)D).
Main Results:
- Infants received low vitamin D intake (64 IU/day), below AAP recommendations.
- Bidirectional changes in serum 25(OH)D observed, dependent on baseline levels.
- Strong inverse correlation between cord blood 25(OH)D and Δ25(OH)D (r = -0.745, p < 0.001).
- Identified an equilibrium point of ~21.4 ng/mL for serum 25(OH)D.
Conclusions:
- First quantitative description of short-term neonatal 25(OH)D changes post-birth.
- Suggests dynamic physiological regulation of vitamin D in early life.
- Highlights the influence of initial vitamin D status on postnatal levels.
Background & Aims:
Little is known about short-term vitamin D dynamics during the immediate neonatal period. Most neonatal studies have relied on single-point measurements of 25-hydroxyvitamin D (25(OH)D), limiting understanding of early postnatal changes. In Japan, healthy full-term infants typically remain hospitalized for 4-5 days, receiving minimal vitamin D intake from small amounts of formula and experiencing virtually no sunlight exposure. This clinical setting provides a unique opportunity to investigate early postnatal vitamin D dynamics under conditions of minimal exogenous input. This study aimed to examine short-term changes in serum 25(OH)D from birth to day 4 of life (Δ25(OH)D) and determine how baseline vitamin D status influences these changes.
Methods:
We analyzed 40 infants with paired cord blood and day 4 serum 25(OH)D measurements obtained by chemiluminescence immunoassay. Linear regression evaluated the association between cord blood 25(OH)D concentrations and Δ25(OH)D.
Results:
Estimated vitamin D intake during hospitalization was 64 ± 18 IU/day, substantially below the 400 IU/day recommended by the American Academy of Pediatrics. Baseline-dependent bidirectional changes in serum 25(OH)D were observed: infants with lower cord blood concentrations increased, whereas those with higher baseline concentrations declined. Cord blood 25(OH)D concentrations were strongly inversely correlated with Δ25(OH)D (r = -0.745, p < 0.001). Regression analysis indicated an equilibrium point of approximately 21.4 ng/mL, at which no net change in serum 25(OH)D was expected.
Conclusion:
This study provides the first quantitative description of short-term changes in neonatal 25(OH)D after birth and suggest dynamic physiological regulation of vitamin D during early life.
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