Objective: The aim of this study was to determine, retrospectively, the serum 25OHD and calcium concentrations of screened neonates of mothers at high risk of 25OHD deficiency (maternal 25OHD < 25 nmol/L or unknown vitamin D concentrations and risk factors for vitamin D deficiency) and critically analyse whether their measurements contributes to the management of these neonates.
Methods: Serum 25OHD and calcium concentrations from 600 samples of umbilical cord blood or venous blood collected from neonates over a 12-month period were analysed. 25OHD concentrations were reported for all while both the corrected calcium concentrations and vitamin D concentrations were available for 569 samples.
Results: There was little or no evidence of association between neonatal 25OHD concentrations and gender, gestational age or birth weight. There was a high prevalence of vitamin D insufficiency (27.6%, 30–50 nmol/L) and deficiency (21.3%, < 30 nmol/L) in neonates from high-risk maternal groups. There was a statistically positive but weak correlation (ρ = 0.22, P < 0.0001) between serum calcium and 25OHD concentrations. Only 7 neonates out of 569 (1.2%) had calcium levels in the hypocalcaemic range; however, a significant number (47.6%) were reported to be in the hypercalcaemic range. Nearly all of these were venous samples collected in first 24 hours after birth. We calculated the reference interval for corrected calcium from our data of venous samples in first 24 hours and the upper limit was significantly higher (2.38–3.04 mmol/L) than the standard reference range used.
Conclusion: Vitamin D deficiency is prevalent in neonates of high-risk mothers but the risk of hypocalcaemia due to vitamin D deficiency at birth is low. Screening neonates entails blood testing which can cause distress to neonates and their parents, substantial impost on staff and financial burden on the health care system. 25OHD deficiency is corrected relatively easily in neonates with supplementation and vitamin D supplementation of neonates from birth without routine screening appears to offer better value of care. Also, the data from this study suggest that the paediatric reference range for corrected calcium concentrations in neonates is higher and the paediatric reference range should be reconsidered.