Background: It is assumed tkat pregnancy and specially labour are accompanied by an increased production of reactive oxygen and nitrogen species (RONS). Oxidative stress can be one of the contributing pathogenetic factors (if not the major) of several diseases of mother and child (e. g. preeclampsia, eclampsia, sudden infant death syndrome, bronchopulmonary dysplasia, retinopathy of prematurity, hypoxic-ischaemic cerebral injury and many others). However, development of an antioxidant defence during pregnancy and changes during physiological labour are not yet known properly. Materiál and methods: We collected heparinised peripheral venous blond samples form healthy mothers in the lat (unti199th day of pregnancy) and the 2°a trimester (between 100th and 192th day of pregnancy), before normal (vaginal) delivery (during regular contractions) and 30 minutes after delivery of the newborn. Heparinised blond from children was obtained from the umbilical cord immediately after delivery. Children small for gestational age (SGA) and preterm were excluded. Samples during the pregnancy were collected by two private gynaecologists and obstetricians, samples from labour were acquired by the Department of Gynaecology and Obstetrics of the Medical Faculty of Charles University in Pilsen. Levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity (AOC) were measured in the Department of Clinical Biochemistry and Laboratory diagnostice of the Medical Faculty of Charles University in Pilsen. To determine these levels (except of TBARS) we used commercial sets produced by RANDOX (Crumlin, North Ireland) and OXIS (Portland, USA), the levels of TBARS were obtained using the thiobarbituric acid reaction (modification by Jentzsch). Results: We examined 21 healthy mothers during pregnancy + labour and their children immediately after delivery. 30 healthy, non-pregnant women served as controls. Mothers vs controls showe lower activities of SOD during the whole pregnancy and labour (p<0.001), increased GPx in the lat and 2°a trimester (p<0.05), decreased levels of GSH during the whole gestation and labour (p<0.05), AOC decreased in the lna trimester (p<0.001) and increased after delivery (p<0.05) and TBARS increased before and after delivery (p<0.05 and p<0.001 resp.) vs controls. However, there was a decrease in AOC in the lna trimester (p<0.05) and increased AOC before and after labour vs AOC in the lat trimester (p<0.05). SOD aktivity decreased before and after delivery vs levels in the lat trimester (p<0.05), TBARS were markedly increased before and after the delivery vs the lat and the lna trimester (p<0.05). The levels of GPx decreased before and after delivery vs levels in the lna trimester (p<0.05). Mothers before vs after delivery showed no significant changes. Newborns had higher levels of TBARS vs TBARS levels of their mothers during the entire pregnancy and labour (p<0.001). GPx decreased (p<0.001), GSH and AOC increased (p<0.001 and p<0.001 resp.) vs corresponding levels of mothers both before and after delivery. Conclusion: A normal pregnancy induces GPx activity and reduces levels of SOD, GSH and AOC. Physiological vaginal labour is associated with a rise of AOC and TBARS and a fall of SOD and GPx in mothers. A physiological vaginally delivered newborn baby is characterized by relatively (vs. their mothers) high levels of TBARS, GSH and AOC and lower activity of GPx. Apgar score and pH of umbilical blond dnes not correlate with either of measured markers of oxidative stress.

        Key words: pregnancy, delivery, antioxidant defence system, mother, newborn.