The congenital defects can be caused by hereditary and environmental factors. One of the most important environmental factors is the exposure to certain chemicals during pregnancy. MTBE (Methyl Tertiary Butyl Ether) is widely used in the fuel industry and enters into the environment, air water with the emissions from cars and leaking of fuel storage tanks. This study is experimental. In this study, 100 rats of the Wistar race were purchased from Razi Institute and were transferred to animal room of Veterinary Faculty of Islamic Azad University, Science and Research Branch, Tehran. They were allowed to adapt with their new surroundings. After 15 days getting ensured that female rats are not pregnant, four female and one male rats were placed in a cage for mating. The mixture of MTBE 50% was prepared with corn oil and the gavages were carried out to each group. On the 18th day of pregnancy the pregnant rats were etherized and the fetal were removed from the abdomen by a gap. Each group was studied considering the number and weight of fetal and also CRL (Crown-Rump Length). The weight of fatal belonging to each animal in each group was measured by digital scale. Also the CRL was measured and recorded by CRL method. The fetal were put in glasses that contained formalin 10% as fixative. The abnormalities in limbs of fetal were then studied by stereomicroscope. Some fetal from each of four groups were stained by alician blue and alizarinred. A number of fetal were also evaluated for changes in liver and kidney using H&E method. Fetal weight evaluation showed a marked reduction assumed as decreased fetal height and growth. The comparison among mean weights of treatment groups and the control group showed a significant difference. Also, the number of alive fetal was decreased among treatment groups. There were cell injury and marked degenerations in proximal tubules of the kidney in group 2 and 3 assumed as disintegrated epithelium and unusual spaces. Also the dilatation glomeruli were observed in histopathological evaluation. Results of histopathological study of fetal liver tissue also showed inactive congestion in lobules and focal necrosis.
