Industrial pig farms involve intensive use of sows with high genetic potential to produce the highest possible number of viable piglets. Developing against the background of an imbalance of peroxide reactions and antioxidant protection, oxidative stress is the cause of postpartum diseases in sows, which lead to a decrease or cessation of milk secretion, high morbidity and death of newborn piglets. The aim of the work was to study different levels of metabolic status in pregnant sows in the norm and in the event of postpartum endometritis in them. The article presents the studies on the indicators of the antioxidant defense system, nitric oxide and endogenous intoxication in sows during gestation. The study included sows of 3-4 farrowings. The sows were included after farrowing, on the basis of a clinical examination, were divided into two groups: clinically healthy and with signs of postpartum endometritis. On day 38-40 of gestation, the state of physiological oxidative stress was established in sows of both groups. On days 78-81 of gestation, they noted a decrease in the accumulation of proteolysis products and activation of the enzymatic and nonenzymatic components of the antioxidant system. At the same time, in sows with endometritis, compared with healthy animals, an increased content of malondialdehyde, medium molecular weight peptides and medium-weight molecules, reduced activity of catalase, glutathione peroxidase, vitamins A, E, and C were revealed in all periods of the study. They also had a high level of stable nitrogen metabolites involved in the development of oxidative stress and in the mechanisms of antioxidant protection.