Purpose: The primary objective of this study was to compare clinical outcomes of very low birth weight (VLBW) infants with 25-hydroxy vitamin D [25(OH)D] levels <25 nmol/l in umbilical cord blood versus VLBW infants with 25(OH)D levels in cord blood >25 nmol/l. The secondary objective was to evaluate umbilical cord vitamin D as a risk factor for respiratory distress syndrome (RDS) in preterm infants.
Methods: We examined 25(OH)D levels in umbilical cord blood and in infants' serum at discharge from the neonatal intensive care unit. We evaluated the associations between severe vitamin D deficiency and various laboratory findings and clinical outcomes.
Results: Eighty one infants with birth weight less than 1500 g met the entry criteria for this study and were divided to groups according to umbilical cord blood vitamin D [Group A: 25(OH)D < 25 nmol/l; 10 ng/ml and Group B: 25(OH)D > 25 nmol/l; 10 ng/ml]. Overall, 81.5% of the infants had a 25(OH)D level <50 nmol/L and 44.4% had a level <25 nmol/L. The laboratory findings and the subsequent clinical outcomes were comparable in infants in both groups (non-significant difference). Only the infants in the 25(OH)D 25 nmol/L group had a lower calcium in urine at age 28 d (p=.0272). In addition, we found in this study that umbilical cord vitamin D level does not lead to a higher or lower risk of RDS (odds ratio 1.044; 95% confidence interval 0.349-0.88; p=.0771).
Conclusions: In our prospective cohort study, we found no significant association between vitamin D status and selected clinical outcomes when using a cut-off of 25 nmol/l (severe vitamin D deficiency) in preterm infants.
Keywords: 25-hydroxyvitamin D; Vitamin D; clinical outcome; prematurity; preterm infants.