Ultrasound is safe during pregnancy but it does not have the same high resolution as the MRI.The current guidelines of the FDA require labeling of the MRI devices to indicate that the safety of MRI with respect to the fetus "has not been established". Safety concerns arise with respect to both mother and fetus. Maternal safety concerns are the same as fora non-pregnant patient, and are addressed by pre-scan screening. Fetal concerns are twofold; first, the possibility of teratogenic effects, and second, the possibility of acoustic damage. In general, it should be noted that most studies evaluating MRI safety during pregnancy show no ill effects.If you are pregnant or suspect you are pregnant, you should inform the MRI technologist and/or radiologist during the screening procedure before the MRI examination. In general, there is no known risk of using MRI in pregnant patients. However, MRI is reserved for use in pregnant patients only to address very important problems or suspected abnormalities. In any case, MRI is safer for the fetus than imaging with x-rays or CT.The changing radiofrequencies and magnetic fields theoretically can produce heat, but this is not known to produce any side effects at all. The risk to a developing baby in the first third of pregnancy is theoretical only, but current advice is that women should not be scanned during the first 13 weeks of pregnancy.
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