Preeclampsia (PE) is a pregnancy specific disorder characterized by high blood pressure and proteinuria after 20 weeks of pregnancy. Despite wide studies on the pathogenesis of preeclampsia, the exact mechanism of this disease is still unknown. Oxidative stress and genetic variation may all be important. Oxidative stress is known as one of the most important factor that plays a significant role in pathogenesis of preeclampsia. However, it seems that oxidative stress caused by an imbalance between toxic compounds such as lipid peroxides and reactive oxygen species might be contribute to the pathophysiology of this disease. Microsomal epoxide hydrolase (EPHX1) play an important role in the hydrolysis of endogenous and exogenous epoxides. So this enzyme is important in the pathogenesis of this disease. Some variations in the sequence of this gene may increase the risk of some disease such as preeclampsia polymorphisms in coding region of microsomal epoxide hydrolase gene change enzymes detoxifying activity. So, functional polymorphisms in the EPHX1 gene may produce toxic intermediates that could be involved in development of pre-eclampsia. In this study, we investigated the association between polymorphism in exon 4 EPHX1 gene with preeclampsia in two group of women with preeclampsia and healthy women in pregnancy as case-control study. In this study, 70 healthy pregnant women, as control group and 70 women whit preeclampsia as case group admitted to Imam Khomeini hospital were selected and 2 ml of blood were collected. EPHX1 genotyping was performed by PCR-RFLP method. Some bioinformatics tools was applied for evaluation of aforementioned polymorphism on the protein structures. Our data showed that the AG genotype (with OR: 0.727, 95% CI: 0.350-1.509, p=0.392), GG genotype (with OR: 0.293, 95% CI: 0.529-2.923 p=0.296) were not associated with preeclampsia. In addition, the data from bioinformatics analysis revealed that this transitions may affect some aspects of the
