Pyrethroids are a group of insecticides that are widely used in agronomy, veterinary medicine and household. It has been recognized that pyrethroids can act as endocrine disruptors, and the intermediate mechanism of exposure and effect on human health can be oxidative stress, characterized by a disturbance in the balance of prooxidants and antioxidants. The well known synthetic pyrethroid is α-cypermethrin, which due to its lipophilic nature accumulates in fatty tissue, liver and brain, but there is also the possibility of its passage through the placenta. The aim of this research is to determine the impact of exposure to α-cypermethrin on the induction of oxidative stress by measuring respective markers in the tissues of female rats exposed to the pesticide in doses of 1, 10 and 19 mg kg-1 day-1 during gestation. We analyzed the concentration of malondialdehyde by high-performance liquid chromatography, and the amount of reactive oxygen species, reduced glutathione, and the catalytic activity of the enzymes catalase, superoxide dismutase and glutathione peroxidase by spectrophotometry in the blood, brain and placentas of female rats. Disturbance of the oxidation-antioxidant balance was observed in all analyzed tissues, mostly after exposure to α-cypermethrin at a dose of 1 mg kg-1. The induction of oxidative stress in the brain of pregnant rats indicates possible physiological damage to the mother, and in the placenta, potential for disruption of the function of the endocrine system.