A 38-year-old pregnant woman at 26-week gestation with left breast cancer requested an FDG PET/CT scan for more detailed staging of her breast cancer before treatment. After discussing the potential radiation-related risk and estimating possible absorbed dose to fetus, she consented for examination. By using a low-radiation-dose CT protocol and administration of routine 370-MBq FDG without diuresis, the resultant calculated (using existing models to predict fetal radiation exposure) fetal dose from CT and FDG would be 3.60 mGy and 6.29 mGy, respectively. In contrast to the existing few literatures, our case also demonstrated previously unreported uptake in the fetal kidneys.