Free radicals (FRs) are molecular species with an unpaired electron in the outer shell, which renders them highly reactive and unstable. FRs containing oxygen may be termed a reactive oxygen species (ROS). The accumulation of reactive FRs, beyond the capacity of the endogenous antioxidant defense system to scavenge them, results in damage to DNA, proteins, and lipids that compromises cell function, leading to cell death via apoptosis or necrosis . Fetal life occurs in a relatively hypoxic environment. Hypoxia is necessary for the development and growth of the fetus. Under normal circumstances, the fetal-to-neonatal transition causes physiological oxidative stress (OS), which enhances the antioxidant defense and pulmonary surfactant maturation .
The oxidant/antioxidant status balance is a process that begins before birth , and premature infants are particularly susceptible to oxidative stress [4, 5]. Most of the complications of prematurity, such as bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), and punctate white matter lesions (PWML), appear related to oxidative stress [6, 7], mostly occurring due to a mismatch among the free radical production and the anti-oxidative capacity of the premature neonate .
Moreover, antioxidant defense mechanisms are incompletely developed or deficient in preterm newborns . Preterm infants show reduced antioxidant defense mechanisms, including decreased levels of vitamin E, β-carotene, melatonin, ceruloplasmin, transferrin, and erythrocyte superoxide dismutase (SOD) . In a study on 100 preterm and 100 full-term neonates, plasma levels of vitamin A, vitamin E, and catalase were found significantly lower while plasma level of MDA, a marker of lipid peroxidation, was significantly higher in the preterm than in the full-term newborns, especially in those ones who developed NEC or BPD . Premature babies have both immature lungs and antioxidant defense systems and often require oxygen supplementation to overcome respiratory distress. The combination of hyperoxia, which enhances the generation of reactive oxygen species (ROS), and low antioxidants cause oxidative stress, inflammation, and even apoptosis, thus increasing mortality and morbidity .
According to the mechanisms of oxidative stress and lack of study in this field, in this prospective study we aimed to compare the levels of serum pro-oxidant/antioxidant balance (PAB) in preterm versus term babies.