| There are no known biological risks from MRI. No delayed sequelae from MR examination have been encountered, and it is expected that the potential risk for any delayed sequelae is extremely small or non-existent. The MR procedure is not believed to be hazardous to the fetus [1-8]. In a survey among female MR workers, no substantial increase in adverse pregnancy outcomes was found . According to the Safety Committee of the Society for Magnetic Resonance Imaging , MR procedures are indicated for use in pregnant women if other non-ionizing forms of diagnostic imaging are inadequate, or if the examination provides important information that would otherwise require exposure to ionizing radiation (i.e., x-ray CT, etc.). It is required that pregnant patients be informed that, to date, although there is no indication that the use of clinical MR procedures during pregnancy produces deleterious effects, according to the FDA, the safety of MR procedures during pregnancy has not been definitively proven .
Also, it is well known that dividing cells, as in the case of the developing embryo during the first trimester, are susceptible to injury from a variety of physical agents. Because of limited data, we avoid MR in the first trimester whenever feasible.
At our institution, for studies performed for clinical indications such as evaluation of an adnexal mass, patients sign an informed consent regarding MR in pregnancy. For studies performed for research indications, institutional review board approval is obtained for the studies, and informed consent is obtained from the patients.
Gadolinium is not recommended for use in pregnancy. Gadolinium has been shown to cross the placenta and appear within the fetal bladder only moments after intravenous administration . From the fetal bladder the contrast is excreted into the amniotic fluid where it is then swallowed, and potentially reabsorbed from the GI tract. Because of this re-absorption, the half-life is of gadolinium in the fetal circulation is not known .
Gadopentate dimeglumine has been shown to retard development slightly in rats when given in doses 2.5 times the human dose and in rabbits (at 7.5 times the human dose) [11, 12]. It is considered a pregnancy category C drug (meaning that it should be given only if potential benefit outweighs the risk) since animal studies have revealed adverse effects but no controlled studies have been performed in humans.
A hidden risk of MR is that of finding an incidental abnormality on MR examination which has unknown significance (Figure). We therefore mention the risk of increased anxiety due to unexpected findings as a risk of the procedure.
|Fig. Fetus at 35 weeks gestational age referred for enlarged cisterna magna. Sonogram was normal (not shown). MRI showed incidental finding of enlarged subtemporal vein (arrow). This is an example of the risk of MR showing an unrelated finding that could increase parental anxiety. The patients were counseled that this was a vascular anomaly that would have gone unrecognized if the MR examination had not been performed. Postnatal outcome was normal at 2 years of age.|
|Our current consent form for research projects states the following:|
|"Some individuals experience claustrophobia when undergoing the magnetic resonance exam. The staff will provide every possible means to reduce this sensation. In the third trimester of pregnancy, it may be uncomfortable to lie on your back for a long period of time. We will attempt to position you comfortably in the magnet and use pillows, as needed. If you feel uncomfortable during the exam, the study can be terminated at any point.
At present, there is no conclusive scientific evidence to support a direct relationship between exposure to MRI and to any hazards to the developing fetus. As fetal cells in the first trimester of pregnancy are susceptible to damage for different types of physical agents, we will only examine patients in the second and third trimester of pregnancy.
It is possible that the confirmatory ultrasound or the MRI will suggest an additional abnormality in your baby, which was previously unsuspected. This may increase your level of anxiety. Counseling about this finding will be available to you from either the radiologist interpreting the study, the perinatologist and/or a genetic counselor."