Objective: The initial development of the fetus occurs in a low-oxygen environment.From the beginning of the second trimester, a high amount of oxygen is required to meet thegrowth requirements such that placenta becomes metabolically active. Under these conditions,oxidative stress (OS) can develop during pregnancy and may result in disorders such as miscarriage and preeclampsia. Although several methods have been used to examine the OS levels ofmother and fetus, the current method is based on assessing the thiol/disulfide balance. In thepresent study, we investigated the thiol/disulfide balance in pregnant women undergoing emergent and elective cesarean sections (CS). Material and Methods: A total of 166 pregnant women,83 in the emergency CS group and 83 in the elective CS group, were included in this observationalstudy. We measured the disulfide, native thiol, and total thiol levels in blood samples collectedfrom the umbilical artery of cords during CS. Results: The native thiol/total thiol ratio was significantly higher and native thiol, total thiol, disulfide, disulfide/native thiol ratio, and disulfide/total thiol ratio were lower in the elective CS group compared with the emergency CS group.Forty pregnant women received general anesthesia (GA), whereas 43 women were administeredspinal anesthesia (SA) in the elective CS group. Women who received GA had significantly lowernative thiol/total thiol ratio. Moreover, they reported a significantly higher total thiol, disulfide,disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol ratios compared withwomen who had SA. Conclusion: Oxidative stress increases in emergency CS, accompanied by asignificant change in the thiol/disulfide balance in favor of disulfides in emergency CS. AlthoughOS levels increased in emergency CS, there was no difference between the groups in terms ofneonatal Apgar scores.