History and Objectives: With popularity of MRI procedures as a diagnostics tool and various reports on its biological effects and in order to determine its effect in the range. 1.5 Tesla on mouse embryonic growth, the present study was conducted in Tarbiat Modares University and Diagnostic Imaging of Imam Khomeini hospital in 1997-1998.

Materials and Methods: An experimental study was carried out on 100 pregnant Balb/c mice. They were divided into 2 groups. Each (50 pregnant mice) group was divided into five subgroups. To one group MRI radiation (1.5 Tesla) was given at the 3, 6, 9, 12 and 15 day of pregnancy. To the second group no radiation was given. The effect of radiation as to numbers of live embryo, dead embryo, absorbed and abnormal embryo was recorded. Other criteria as to the weight, length of embryo, length of right and left femur, bone volume of Tibia with Alizarin Red and Alcian Blue staining were analyzed. Determination of bone volume one day before delivery was determined. T-test and other statistical analysis was conducted on 2 groups.

Results: No apparent abnormality was observed in two groups. The number of dead and absorbed embryos at the 9 and 12 embryonic day was higher in radiated group compared to the control group however the difference was statistically insignificant. At the 9 and 12 embryonic day, the weight of embryo was 30.2% and 18.1%, height of embryo 17.6% and 12.7% length of right femur 24.9% and 14% and the left femur 25.4% and 16.9% and volume of left Tibia was 32% and 23.8% of the control group. These differences were statistically significant (P<0.05), whereas for other days no significant difference was observed.

Conclusion: MRI has an effect at the 9 and 12 day of mice embryonic life. Further study on the effect of MRI on human models is recommended.