Vitamin D Status of Preterm Newborns at Approximately 4 Weeks of Age in Shenzhen, China: A Retrospective Observational Cohort Study Conducted Across Two Centers

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Background and Objectives:To examine the correlation between the concentration of vitamin D (VD) in venous blood at approximately 4 weeks of age (±4 weeks of age) and neonatal outcomes in preterm infants (birth weight <1500 g or gestational age <32 weeks) in two neonatal intensive care units (NICUs) located in Shenzhen, China.Methods and Study Design: Preterm infants were split into two groups based on their VD concentration at ±4 weeks of age: VD insufficiency (VDI) group (≤20 ng/mL) and VD sufficient (VDS) group (>20 ng/mL).Binary logistic regression analysis was used to examine relationships between outcomes and VDI.Results: Of 230 infants in total, 119 (51.7%) were assigned to the VDI group and 111 to the VDS group (48.3%).No correlation was found between serum VD at ±4 weeks of age and gestational age (p>0.05).The starting point of the two groups for oral VD intake did not differ significantly (p>0.05).At ±4 weeks of age, oral VD dose (P<0.05) was greater in the VDS group.Gestational diabetes mellitus was associated with VDI (OR=1.94,95% CI 1.01-3.75,p=0.047) after controlling for this risk.Following correction for gestational age and oral VD dosage at ±4 weeks old, VDI was also linked to a significant risk of retinopathy of prematurity (OR=2.00,95% CI 1.08-3.68,p<0.027).Conclusion: Preterm newborns (gestational age <32 weeks or birth age <1500 g) in NICUs in Shenzhen, China continue to have significantly high VDI.Higher VDI is associated with gestational diabetes mellitus and retinopathy of prematurity.