en ویروس شناسی Virology پژوهشي Research <strong>Background and Aims:</strong> Almost 350 million people worldwide are carriers of hepatitis B virus. The rate of chronic carriers in Iran is about 3%.&nbsp; Therefore Iran is categorized as a country with moderate rate of infection with this virus. In developing countries, transmission from mother to fetus and newborn is considered as one of the main routes of transmission. So, this study investigated the prevalence of hepatitis B and its risk factors in pregnant women.<br> <strong>Material and </strong><strong>Methods: </strong>In this descriptive cross-sectional study which has been done in 2010-2011, of 759 pregnant women referred to the Central Laboratory of ACCER and laboratory of Mashhad Ghaem hospital for HBsAg testing, after obtaining consent form, patients entered to the study with simple non-probability sampling, and a questionnaire was completed about demographic characteristics and related factors<strong>.</strong> Then data were analyzed by SPSS ver.13<strong>. </strong><br> <strong>Results:</strong> The mean age of participants was 28.16 &plusmn; 4.8, the prevalence of HBsAg among pregnant women was reported 0.3%, and also because of finding only two cases of HBsAg positive, significant association was not found with <em>socio-demographic</em> factors such as; vaccination history of hepatitis B (<em>P= 0.527</em>) and risk factors including family history of hepatitis B or hepatitis C (<em>P= 0.999</em>)<strong>. </strong><br> <strong>Conclusions:</strong> Our study revealed that the prevalence rate of HBsAg positive among pregnant women is low. The prevalence of obtained HBsAg in this study compared to other studies from Iran is low, so, further studies with more cases are necessary to achieve real estimation of HBsAg positive among pregnant women.<br> &nbsp; HBsAg, Pregnant women, Iran HBsAg, Pregnant women, Iran 222 228 http://ijml.ssu.ac.ir/browse.php?a_code=A-10-243-1&slc_lang=en&sid=1 Seyed Javad Pourafzali No Research Center for HIV/AIDS, HTLV and Viral Hepatitis, Iranian Academic Center for Education, Culture and Research (ACECR), Mashhad, Iran. Azad Khaledi No 2 Infectious Diseases Research Center, Kashan University of Medical Sciences, Kashan, IR Iran. 3 Department of Microbiology and Immunology, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran. Rahele Miri No 4 Department of Parasitology and Mycology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Seyed Ali Akbar Shamsian No 5 Department of Immunology, Immunology Research Centre, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Seyed Abdolrahim Rezaee No 6 Autoimmune Diseases Research Center, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran. Ahmad Piroozmand No 7 Antimicrobial Resistance Research Center, Department of Virology and Microbiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Kiarash Ghazvini Yes 7 Antimicrobial Resistance Research Center, Department of Virology and Microbiology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.