Plasma zinc concentration and catch up growth in preterm infants.

Changes in plasma zinc concentration during the period of catch up growth were examined in 44 preterm infants. Blood samples were collected at birth, 6, 12 and 24 weeks. Plasma zinc concentration showed a mean of 13.6 mumol/l at birth and dropped to 9.8 mumol/l at 6 weeks and rose to 11.3 and 15.4 mumol/l at 12 and 24 weeks respectively. Plasma zinc concentrations showed significant correlation with weight velocity at 12 weeks. Male infants had significantly lower plasma zinc concentrations than females at 12 weeks. Infants of gestational age more than 32 weeks had lower plasma zinc concentrations at 12 and 24 weeks than those of earlier gestations. At the same time males were growing faster than females and also infants of gestational ages more than 32 weeks were growing faster than those born at earlier gestations. These observations, together with the finding that the decline in zinc occurred during the phase of rapid growth, suggest that growth is the predominant modulator of plasma zinc concentration.