Pregnant woman can be exposed to ionizing radiation either unintentionally or because the radiologic procedure is indicated during pregnancy. The probability of biological damage to the fetus brings anxiety to the expectant mother and medicolegal responsibility to the doctor. Women in reproductive age should be questioned for possible pregnancy before any radiological imaging procedure. The radiation dose that the fetus receives is different from the dose pregnant woman is exposed. The position at which the image is obtained, fluoroscopic examination, area exposed to X-ray, the thickness of the patient, quality of the beam, irradiation time, the distance between the skin surface and the origin of the beam are important when calculating the dose. The number and the thickness of the sections taken also affect the absorbed dose in computerized tomography. Radiation effects on the fetus depend on both gestational age and probable absorbed dose. The negative effects due to radiation are congenital anomalies, growth retardation, embryonic death, mental retardation and other neurobehavioral effects. There are threshold radiation levels for the negative effects to be seen on the fetus. Different commission statements advice that women should be counselled that exposure to radiation less than 50 mGy is not related with an increase in anomalies. The embryo is rarely expected to be negatively affected if the pregnant woman undergoes examination of head, neck , chest or extremities. However the perception of the risks by the expectant mother and the real risks estimated by doctor may not overlap. To explain the fetal risks with proven numbers on tables of calculated fetal doses would be more satisfying for both the mother and the doctor. Although the borders are not clearly defined yet, this review aims to deal with problems that we can encounter frequently in clinical practice. Copyright © 2011 by Türkiye Klinikleri.