Factors associated with variation in plasma copper levels in preterm infants of very low birth weight.

At 2-weekly intervals from age 4-14 weeks, the possible effects on plasma copper concentration of gestation, multiple birth, fractional weight change from birth (W/BW) and, up to 10 weeks, average daily total copper intake from birth were explored in 43 preterm infants of very low birth weight. There was no significant association between the logarithm of the plasma copper concentration (ln Cu) and multiple birth at any time and no significant association between ln Cu and gestation was found from 4-12 weeks. From age 4-10 weeks, there was a significant negative correlation between ln Cu and W/BW and at 4, 6 and 10 weeks there was also a significant negative correlation between ln Cu and copper intake. W/BW and copper intake were correlated throughout. At 14 weeks, ln Cu correlated positively with gestation and negatively with W/BW but, at this age, gestation and W/BW were correlated. The maximum total variation (R2) in ln Cu explained by its regression on gestation, multiple birth, W/BW and/or copper intake combined was only about 31% (at 10 weeks). The potential for copper depletion may be greater in rapidly growing infants.