Background: Investigation of toxicity of silver nanoparticle, especxially blood toxicity, is necessary because this nanoparticle is used a lot in diffrerent parts of life and invironment. The aime of this is evaluation the effects of silver nanoparticles with different concentrations on blood cells pregnant Wistar rats.

Materials and Methods: In this case control study, 30 pregnant rat were divided into 5 experimental groups (three treatment groups, one control group, and one injection control group). Treatment and Control groups received different concentration of silver nanoparticle (250, 500, and 1000 ppm) and normal food and water conditions during the experiment, respectivelly for 18 days. After this rime, rats were investigated in terms of blood cells.

Results: The results showed that being treated with silver nanoparticles led to significant reduction of RBCs at the concentrations of 500 and 1000 ppm (p <0.05). In 250 ppm, silver nanoparticles showed no significant reduction. WBCs had significant changes in 1000 ppm concentrations compared to control group. In lower concentration, the amount of WBCs was incresed. This data showed that silver nanoparticles can active the immune system as alergic agents.

Conclusion: Based on results, silver nanoparticles revealed toxic effects on blood cells in high concentration (1000 ppm). So, these nanoparticles must be used with more caution.