Serum zinc and copper levels in infants admitted to the neonatal intensive care unit

Abstract

ObjectivesZinc and copper are trace elements, but their reference values during the neonatal and infant periods are not clear. We aimed to determine the trend of serum zinc levels in infants admitted to the neonatal intensive care unit and compare serum zinc and serum copper levels at admission between small-for-gestational-age (SGA) and non-SGA infants. MethodsFrom 406 patients admitted to the neonatal intensive care unit from January 2009 to September 2012, 339 patients were included in this retrospective study. Blood samples were collected on admission, and serum zinc and serum copper levels were measured. Serum zinc was tested every month until discharge. ResultsSerum zinc levels of infants born at <30 wk of gestation decreased by 46% in the first month of life. All infants born at ≤34 wk of age became zinc deficient at 2 mo of age. The relationship between gestational age and serum zinc level at admission had a negative correlation (Spearman's rank correlation cofficients) = –0.66; P < 0.001). There was a negative correlation between serum zinc and serum copper at admission (rs = –0.49; P < 0.001). Serum copper levels of SGA infants at admission were significantly higher than those of non-SGA infants (P < 0.001). ConclusionsAll of the infants admitted to the neonatal intensive care unit at ≤34 wk of gestation were zinc deficient by 2 mo of age, suggesting the need for enteral zinc administration. Serum copper was higher in SGA infants than in non-SGA infants on admission, but further studies are needed to determine whether excess copper affects development.