The peripartum period and delivery are considered critical for maintaining a balance between the production of free oxygen radicals and functional incompetence of the antioxidant system of a foetus and a neonate.

Objective:
The aim of the study was to evaluate the oxidoreductive state of mothers and their newborns immediately after delivery and in the first few days after birth.

Material and Methods:
Eighty-five mothers and their healthy, term newborns were included into the prospective study. Total antioxidant capacity (TAC) and thiobarbituric acid reactive substances (TBARS) in maternal placenta and milk, as well as blood and urine of the neonates on the first and third day after birth, were examined.

Results:
Elevated levels of TBARS were found in maternal placenta and neonatal blood on the third day after birth, but low concentrations were observed in maternal milk. On the contrary, total antioxidant status (TAS) showed a declining tendency in neonatal blood and an increasing tendency in breast milk. Markers of oxidative stress and antioxidant capacity were independent of the mode of delivery.

Conclusions:
Values of oxidative stress markers in mothers and newborns immediately after birth were elevated and increased further during the first few days of neonatal life. Breast milk was the only nutritional substance with high antioxidant activity. At the same time, TBARS levels in breast milk decreased, which might indicate its protective role in reducing oxidative stress in newborns.