Aim. The aim of the study was to investigate the functional state of the «lipid peroxidation - antioxidant defense» system in the peripheral blood of parturients with mild and severe COVID-19.Materials and methods. This casecontrol study examined 95 parturients with confirmed COVID-19 diagnosis in the third trimester, divided into two groups based on the severity of the disease. Group 1a included parturients with severe COVID-19 (community-acquired pneumonia, n=48), while group 1b consisted of patients with mild COVID-19 (acute respiratory viral infection, n=47). The control group was composed of 45 parturients without a prior or current diagnosis of COVID-19. The average age of women in the study groups was 23.9±0.50 years, and 24.4±0.60 years in the control group (p>0.05). Peripheral venous blood served as the material for the study. Spectrophotometric methods were used to examine the concentrations of primary (diene conjugates - DC) and final (active thiobarbituric acid products - TBARS) products of lipoperoxidation. The content of 8-isoprostane, total antioxidant capacity of plasma components, and phospholipase A2 were investigated using enzymelinked immunosorbent assay (ELISA).Results. Study showed that parturients with severe COVID-19 had increased levels of phospholipase A2 by 2.1 times (p<0.001), oxidative stress markers: diene conjugate concentrations by 1.94 times (p><0.001), TBARS by 2.2 times (p><0.001), and 8-isoprostane by more than 2 times (p><0.001), along with a simultaneous decrease in the total antioxidant capacity of blood plasma components by 1.7 times (p><0.001) compared to the control group. In the group of parturients with mild COVID-19, the studied indicators changed less significantly. Conclusion. The study established the pathogenetic role of SARS-CoV-2 in disrupting the functional system of «lipid peroxidation - antioxidant defense» and the development of oxidative stress in parturients who had COVID-19 in the third trimester. A dependency of oxidative stress marker concentrations in peripheral blood on the severity of COVID-19 was identified. It was shown that COVID-19 in the third trimester of pregnancy is associated with high levels of phospholipase A2, an imbalance in the prooxidant-antioxidant system, characterized by a reduction in the level of total antioxidant capacity and an increase in oxidative modification products of biomolecules, expressed by the growth of DC, TBARS, and 8-isoprostane levels, leading to oxidative stress correlated with the severity of lung damage. Key words: COVID-19, parturients, lipid peroxidation, antioxidant defense, oxidative stress> ˂ 0.001), oxidative stress markers: diene conjugate concentrations by 1.94 times (p ˂ 0.001), TBARS by 2.2 times (p ˂ 0.001), and 8-isoprostane by more than 2 times (p ˂ 0.001), along with a simultaneous decrease in the total antioxidant capacity of blood plasma components by 1.7 times (p ˂ 0.001) compared to the control group. In the group of parturients with mild COVID-19, the studied indicators changed less significantly.Conclusion. The study established the pathogenetic role of SARS-CoV-2 in disrupting the functional system of «lipid peroxidation - antioxidant defense» and the development of oxidative stress in parturients who had COVID-19 in the third trimester. A dependency of oxidative stress marker concentrations in peripheral blood on the severity of COVID-19 was identified. It was shown that COVID-19 in the third trimester of pregnancy is associated with high levels of phospholipase A2, an imbalance in the prooxidant-antioxidant system, characterized by a reduction in the level of total antioxidant capacity and an increase in oxidative modification products of biomolecules, expressed by the growth of DC, TBARS, and 8-isoprostane levels, leading to oxidative stress correlated with the severity of lung damage.