LIPID-PEROXIDATION IN CORD-BLOOD AT BIRTH - THE EFFECT OF LABOR

Objective To determine the effect of labour on free oxygen radical act ivity in the fetus, as reflected by lipid peroxide levels in umbilical cord arterial blood. Design Prospective, observational study. Setting Department of Obstetrics and Gynaecology, The Chinese University of H ong Kong. Methods Umbilical cord arterial and venous blood samples wer e collected from singleton term infants delivered by elective caesarea n section. Base excess, pO(2), pCO(2) and pH were measured in both sam ples and compared to identify double venous samples. Cord arterial aci d-base balance and concentrations of organic hydroperoxides and malond ialdehyde were compared with those obtained from normal vaginal delive ries. Results Cord arterial blood samples, obtained from cases of unco mplicated labour followed by spontaneous vaginal delivery, had signifi cantly higher lipid peroxide concentrations than those delivered follo wing elective caesarean section. This was most marked for malondialdeh yde with a median value increased by 105%, whilst organic hydroperoxid e was increased by only 27%. Of the acid-base parameters, base excess was increased by 78%, with only minimal changes in pH, pCO(2) and pO(2 ). These differences remained highly significant after including other pregnancy characteristics in multivariate analysis. Conclusion The fi ndings indicate that high levels of free oxygen radical activity in th e fetus are a function of the labour process, as are changes in acid-b ase balance.