Bilirubin and ascorbate antioxidant activity in neonatal plasma.

Extremely low birth weight premature infants have been known for many years to have limited antioxidant protective capacity, especially with reference to those antioxidant components which do not cross the placenta until the third trimester of gestation. In this study the total antioxidant activity and the concentrations of individual antioxidants in plasma from premature neonates (27 +/- 2 weeks gestation) compared to term babies (38-41 weeks gestation) have been examined. The results show elevated levels of ascorbate at birth in the plasma of premature neonates compared with those of term babies, but the total plasma antioxidant status of the premature babies is significantly lower than that of term babies. At 5 days post-partum the ascorbate levels are within the normal adult range and plasma bilirubin levels are considerably enhanced in both groups, while the total plasma antioxidant status of the premature neonates has increased. Analysis of the relationship between the total plasma antioxidant activity and the bilirubin concentration show a direct, highly significant correlation for the term group, r2 = 0.774, consistent with significance of bilirubin as a plasma antioxidant.