Introduction & Objective: During recent decades so many researches have been engaged to assess the relation of electromagnetic fields with different powers on prevalence of fetal developmental disorders, sterility, advent of nervous and sleeping disorders, gastrointestinal and cardiovascular mortality, variety of neoplasm’s and among the rest hematopoietic and lymphatic tissue neoplasm's and even hematopoiesis disorders. The results provided by these studies are different and very miscellaneous and the research horizon in this field still is spreading. In this study the effects of low electromagnetic field (LEMF) and the field intensity of 5 militesla (50 HZ) on the numbers of megakaryocytes and the volume of liver in NMRI mice fetus was assessed.

Materials & Methods: This experimental- analytical study has assessed the effect of LEMF (50 Hz) on the number of liver's megakaryocytes and the weight of 66 three months NMRI mice embryos that they were divided into 6 groups. Experimental groups were exposed to LEMF and then randomly an embryo was selected from each mother and its liver was extracted and fixed in formalin. After providing microscopic sections according to stereological methods, cell counting was performed and data were analyzed and verified by common stereological methods and formulas. SPSS (version11.5) software and Kuruskal-Wallis and Chi-square tests were used for statistical analysis.

Results: The number of liver megakaryocytes in all experimental groups comparing to sham and control groups was reduced but the difference was not significant (P>0.05), the most reduction was in 17-21 days of exposure and the least reduction was in group10-14 days of exposure. The embryos weight in all experimental groups comparing to sham and control groups was reduced, however this difference was not significant (P>0.05) and the most difference was related to group 10-14 days of exposure.

Conclusion: The results of this study revealed that in pregnant mice exposed to LEMF irrespective of the length of pregnancy there are not significant changes in the liver volume and the numbers of liver's megakaryocytes in NMRI mice fetus.