In their recent article, Beyeler et al1 conclude that “staging procedures must avoid ionizing radiation” and state that “magnetic resonance imaging [MRI] is harmless to the fetus.” This statement is misleading.
In the United Kingdom, the National Radiological Protection Board (NRPB), now the Radiation Protection Division of the Health Protection Agency, suggests that pregnant women should not be offered MRI in the first 3 months of pregnancy. Although the results of studies on mammals were mostly negative, the National Radiological Protection Board considered it prudent to avoid MRI of pregnant women during the first trimester, until the consequences of exposure to time-varying magnetic field gradients become more clearly established. The radiofrequency fields used during MRI can cause heating effects in the mother and fetus. These, in turn, can cause adverse effects that may be avoidable if the temperatures in the tissues do not exceed 38°C. On this basis, the NRPB concluded that until further information becomes available, pregnant women should not undergo MRI in the first 3 months of pregnancy unless the only reasonable alternative imaging method involves the use of x-ray procedures.