Pobedy, Orenburg, 460018 Russia, e-mail elenka_rs@mail.ru, osipaylova@mail.ru; 2All-Russian Research Institute of Beef Cattle Breeding, Federal Agency of Scientific Organizations, 29, ul. 9 Yanvarya, Orenburg, 460000 Russia, e-mail sizova-l78@ya.ru, vniims.or@mail.ru Acknowledgements: Hematological studies were performed using standard techniques in the Laboratory of Agroecology of Nanomaterials and Test Center of All-Russian Research Institute of Beef Cattle Breeding (accreditation certificate RA. <...> Supported by Russian Scientific Foundation (project ¹ 14-36-00023) Received June 5, 2016 A b s t r a c t Nanoparticles of zinc (Zn NPs) and zinc oxide (ZnO NPs) are considered as materials of low toxicity, as Zn is the most important trace element in human body usually found in food and used as a food additive. <...> Currently, there is a serious lack of information about the potential dangers of nanomaterials (NMs) for mammals, and particularly for human. <...> Moreover, there is not enough information about their potential hazard for reproductive health. <...> The aim of this study is to investigate the potential negative effects of positively charged 90 and 95 nm nanoparticles of zinc (Zn NPs) and zinc oxide (ZnO NPs) on metabolic processes during pregnancy according to morphological and biochemical blood indices, morphofunctional structure of liver and element status in Wistar rats and fetuses. <...> Of blood morphological indices, concentration of erythrocytes (1012/l), white blood cells (109/l), hemoglobin (g/l), hematocrit (%) was estimated. <...> In blood serum ALT (U/l), AST (U/l) and LDH (U/l) activity was assessed. <...> Tissue samples were analyzed on a mass spectrometer Elan 9000 and atomic emission spectrometer Optima 2000 V (Perkin Elmer, USA). <...> The concentration of red blood cells and hemoglobin increased when Zn NPs injected. <...> Increasing activity of enzymes (ALT, AST, LDH) demonstrates the destructive process in hepatocytes of mother rats, which depends directly on the dose and type of the nanoparticles. <...> Generally, the blood parameters confirm a potentially hepatotoxic effect of Zn NPs and ZnO NPs which was shown histologically. <...> Microstructural changes of liver tissue (degeneration and cytolysis <...>