Prenatal radiation exposure
Pregnant women may be exposed to nonionizing, ionizing radiation and contrast media via diagnostic or therapeutic procedures and workplace exposure. When computed tomography or magnetic resonance imaging is performed on a pregnant woman, the effects of exposure to radiation, high magnetic fields and contrast media, which can be risky for a fetus, should be considered. Nonionizing radiation that is not significantly risky for a fetus includes microwave, ultrasound, radio frequency and electromagnetic waves, while ionizing radiation that can be teratogenic, carcinogenic or mutagenic includes particles and electromagnetic radiation. The effects of radiation are associated with the level of exposure and stage of fetal development. Organogenesis (two to seven weeks after conception) and the early fetal period (eight to fifteen weeks after conception) are the most sensitive stages for a fetus. Noncancerous health effects have not been determined at any stage of gestation with less than 50 mGy (5 rad) exposure dose of ionizing radiation. Higher exposure levels may lead to spontaneous abortion, growth restriction, and mental retardation. The risk of cancer is increased regardless of the dose. Although the use of iodinated contrast media is generally thought to be safe during pregnancy, the risk of fetal hypothyroidism should be considered and it should be used only when necessary. The use of gadolinium-based contrast media during pregnancy is controversial because of the lack of clinical data. The purpose of this article is to review the existing literature regarding the prenatal radiation exposure and to discuss fetal risk of radiation.