Abstarct: Embryo and fetus in the uterine is sensitive to ionizing radiation in the whole period of pregnancy prior to birth. Owing to the high sensitivity of the fetus to ionizing and non-ionizing radiation, protecting the pregnant woman and her fetus would be a major challenge. However, many pregnant women are affected (un)consciously by ionizing radiation. In the present study, due to the increasing rate of absorbing rays by the intrauterine and high sensitivity of the fetus to such rays, all phantoms of a pregnant woman in different ages of pregnancy (third month, sixth month, ninth month) were simulated by the MCNPX computer code for calculating the dosimeter of the pregnant woman. ......