Urinary excretion of calcium and phosphate in preterm infants.

The aims of this study were to determine reference ranges for the urinary calcium (UCa/Cr) and phosphate (UPO(4)/Cr) creatinine ratios and to study factors influencing these ratios in a representative population of preterm infants managed according to current nutritional guidelines. Spot urine samples were obtained from 186 preterm infants (gestation 24-34 weeks) for measurement of UCa/Cr and UPO(4)/Cr ratios as part of a routine metabolic bone screening program, once every 2-4 weeks from the 3rd to the 18th week of life. Data were also collected on gender, appropriate or small for gestational age (SGA), nutrition [total parenteral nutrition (TPN), preterm or term formula, and breast milk], plasma Ca, P0(4), urea, and electrolytes and on the use of drugs (frusemide, dexamethasone, and theophylline).