1. In healthy humans, a balance exists between oxygen-derived free-radical production and their removal by antioxidants. In preterm infants inadequate antioxidant defences may contribute to the pathogenesis of some of the complications of prematurity.
2. Plasma total antioxidant status and malondialdehyde concentration were measured during the first 11 days of life in 25 infants to determine whether increased lipid peroxidation is associated with low extracellular antioxidant status. In a second group of infants, total antioxidant status was quantified within 12 h of birth, and subsequently on days 4 and 10 to investigate the hypothesis that adverse neonatal outcome is associated with low antioxidant status.
3. There may be a weak negative correlation between the total antioxidant status of infants and the lipid peroxidation marker malondialdehyde in plasma (r = −0.24, P = 0.056, n = 89) during the first 11 days of life. In the second group of infants, total antioxidant status was found to be significantly related to plasma urate and bilirubin levels, but not to adverse neonatal outcomes such as chronic lung disease, intraventricular haemorrhage, retinopathy of prematurity or death.
4. If adverse neonatal outcomes are due to inadequate antioxidant defences, these are likely to be intracellular or localized rather than general extracellular deficiencies.