Metabolic Bone Disease in Very Low-Birth-Weight Neonates

Background: Metabolic bone diseases (MBD), including rickets and osteopenia, are important neonatal complications among preterm infants. This study aimed to determine the prevalence and risk factors of MBD in neonates with very low birth weight (VLBW). Methods: This prospective study was conducted on VLBW infants from January 2012 to July 2013. Inclusion criteria were birth weight of ≤1500 g and age of ≤7 days, and the exclusion criteria were cholestatic disorders, skeletal anomalies and genetic syndromes. Serum calcium, phosphorus and alkaline phosphatase (ALP) concentrations were measured regularly until the 12th week of birth. In addition, wrist and chest radiographs were obtained from the neonates at 8-12 weeks of age. Results: In total, 58 neonates with the mean gestational age of 30.6±2.65 weeks, weight of 1265±262 g and height of 38.06±2.49 cm were enrolled in this study. The correlation between biochemical parameters in multiple analysis and radiological findings of rickets was examined, and a significant association was observed between serum phosphorus level at the first week of age and the incidence of rickets. Moreover, 14 infants had only one radiologic sign of rickets (e.g. fraying, cupping, widening or lack of provisional zone of calcification (PZC), and 8 subjects (13.7%) showed at least two radiologic signs. The prevalence of osteopenia and rickets among infants with birth weight of <1200 g was 32.7% and 81.8%, respectively. In addition, 72.2% of the neonates with birth weight of >1200 g had normal X-rays (P=0.036). Conclusion: Despite the remarkable advances in the management of VLBW infants, MBD is still a prevalent complication during the neonatal period. According to the results of this study, birth weight and gestational age are the most significant risk factors for MBD.