Normal values for plasma creatinine concentration related to maturity in normal term and preterm infants.

Creatinine concentration was measured by a kinetic method in 475 plasma samples obtained from 260 term and preterm infants during the first 2 months post-natal age. In term infants plasma creatinine fell from 88 +/- 4.4 mumol/L (mean + SEM) at birth, to 60 +/- 1.9 mumol/L by the fourth day remaining stable thereafter; in preterm infants creatinine fell to 86 +/- 7 mumol/L by the fourth day. Analysis of pooled data from all infants of more than 4 days post natal age revealed a progressive fall in creatinine with increasing post conceptual age. The normal range of values varies with post conceptual age and was not influenced by gestational age at the time of birth.