Abstract: The fetus magnetic resonance imaging (MRI) at 1.5 T is permitted at clinic when the MRI scan is really necessary for the pregnant women with more than three months pregnancy. However, the relevant studies about the safety of MRI scan for pregnant women at 3 T have not been thoroughly implemented. With the rapid increase of 3 T MRI system at clinic, the related studies are necessary to exploit the advantage of 3 T MRI system. In this paper, the finite difference time domain method was utilized to calculate the specific energy absorption rate (SAR) and the B₁ field within pregnant woman pelvis. The electromagnetic model of pelvis was built in accordance with medical image and international standard. The B₁ field homogeneity and the SAR distribution were respectively analyzed using birdcage coil at 1.5T and 3T systems. The numerical results indicate that the average SAR and the maximum local SAR were maximally increased 2.79 times and 3.96 times respectively from 1.5T to 3T and the maximum local SAR of skin and amniotic fluid at 3T exceeds the safety threshold. The uniformity of B₁ field was reduced by 19%, 25%, and 21% within the pregnant woman uterus region on three selected sections. The homogeneity of the B₁field inside the uterus at 3 T is less than 67%. The results indicate that the local SAR and the inhomogeneity of B₁field are the main constraints for the application in the fetus MRI scan at 3T.