MRI in pregnant patients is appropriate when the benefits outweigh the risks as assessed by a Radiologist
Risks of MRI for the pregnant patient
- Patients in the first trimester of pregnancy might be more susceptible to potential adverse effects, although several studies have been conducted and have shown no evidence of injury or harm to the fetus at field strengths of 1.5 T or less.1,2
- Theoretical concerns include:1,2
- possible bioeffects of the static magnetic field,
- risks associated with exposure to gradient magnetic fields, especially acoustically related safety issues,
- potential adverse effects of radiofrequency (RF) energy and heat deposition in tissue, and
- possible adverse effects related to the combination of all three magnetic fields.
- The safety of MRI at field strengths higher than 1.5 T (i.e., 3 T, 7 T) during pregnancy has not been thoroughly assessed.2
- To date, there has been no indication that the use of clinical MR imaging during pregnancy has produced deleterious effects in scanners operating up to and including 3-Tesla.
- In order to properly assess risk with regard to pregnancy, it is recommended that every patient of childbearing age is asked before a procedure if there is a possibility that they may be pregnant (also see related guideline Pregnant patients).
- Questions regarding the date of the last menstrual period, pregnancy, or late menstrual period should be included as part of comprehensive MRI screening.1
- A definite or possible pregnancy must be identified prior to permitting the patient into the MRI environment so that the risk vs. the benefit of the MRI procedure can be considered and discussed with the patient.1
Appropriate use of MRI for pregnant patients
- A pregnant patient and their fetus may require imaging for many different reasons that may or may not be related to the pregnancy. Imaging remains an essential tool to provide the best possible care to many pregnant patients.5
- MRI may be used in pregnant patients 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.1
- Before proceeding with MRI, the healthcare team considers questions such as:
- Is the MRI procedure appropriate to address the clinical question? 1
- Is it possible to delay the exam until after delivery?
- Would sonography be satisfactory for diagnosis? 1
- Is early delivery a consideration? 1
- MRI should not be withheld when the benefits of the examination clearly outweigh the risks, such as, but nor limited to, the following cases:1,2
- Brain and spine symptoms requiring imaging
- Cancer requiring imaging
- Chest, abdominal and pelvic signs and symptoms of active disease where sonography results are inconclusive
- Specific, suspected cases of fetal anomaly or complex fetal disorder
Obtaining informed consent
- The patient has the right to be informed regarding the procedure/treatment and its risks in a way that they can understand and can received answers to any questions they may have (see Informed Consent guideline).
- Pregnant patients receiving an MRI in scanners operating up to and including 3-Tesla should be informed that, “to date, there has been no indication that the use of clinical MR imaging during pregnancy has produced deleterious effects.” 1
- It is recommended that informed consent from the patient or guardian is obtained by the radiologist, prior to the MRT initiating the exam.6,7
MRI with contrast
- Gadolinium enhancement is best avoided when examining the pregnant patient.1,2
- Research on the risks posed by gadolinium-based contrast for pregnant patients is limited, and there is insufficient evidence to conclude that it poses no risk to the fetus.1
- In a retrospective review of Ontario’s provincial database of births, a study concluded that the risk of a congenital anomaly did not differ between patients exposed to gadolinium-based contrast agents (GBCAs) at any time during pregnancy and those patients who did not undergo MRI.8–11
- The study also found that exposure to GBCAs at any time during pregnancy was associated with an increased risk of stillbirth or neonatal death, although the number of deaths in the exposed group was small.8–11
- A large scale study by Bird ST, Gelperin K, Sahin L, et al. (2019), the research highlighted that increased screening and vigilance may be warranted when administering GBCAs to potentially pregnant patient populations.2,12
- The study identified higher rates of gadolinium-based contrast agent (GBCA) exposure during the first few weeks of pregnancy compared with the later weeks of pregnancy, suggesting inadvertent exposure to GBCAs might occur before pregnancy is recognized.12
- If a GBCA is to be used in a pregnant patient, one of the agents believed to be at low risk for the development of (nephrogenic systemic fibrosis) NSF should be used at the lowest possible dose to achieve diagnostic results.9
- If it is absolutely necessary to proceed using a contrast agent, a consent form is signed by the patient following an informed consent process which includes an explanation of the potential risks and benefits by the radiologist.9
Counseling
- Pregnant patients are informed that current data shows MRI to be relatively safe for pregnant individuals with no evidence of deleterious effects in the literature.1
- If the patient is to undergo a procedure requiring gadolinium-based contrast, an explanation is provided regarding the risks of contrast media and the precautions that are being undertaken to avoid unnecessary exposure to risk. 7
References
- Shellock FG. Reference Manual for Magnetic Resonance Safety, Implants, and Devices. Biomedical Research Publishing Group; 2020. Accessed August 7, 2020. http://www.mrisafetybook.com/
- ACR Committee on MR Safety. ACR manual on MR safety. Published online 2020. Accessed August 7, 2020. https://www.acr.org/-/media/ACR/Files/Radiology-Safety/MR-Safety/Manual-on-MR-Safety.pdf
- Martensen K. Radiographic Image Analysis. Saunders Elesvier; 2011.
- Health Canada. Safety code 35: Safety procedures for the installation, use and control of x-ray equipment in large medical radiological facilities. Published online 2008. Accessed August 7, 2020. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/radiation/safety-code-35-safety-procedures-installation-use-control-equipment-large-medical-radiological-facilities-safety-code.html
- Radiological Society of North America. RSNA Statement on Safety of the Developing Fetus in Medical Imaging During Pregnancy. Published online 2018. Accessed March 3, 2021. https://www.rsna.org/uploadedfiles/rsna/content/role_based_pages/media/rsna-imaging-during-pregnancy-statement.pdf
- Royal Australian and New Zealand College of Radiologists. Medical Imaging Informed Consent Guidelines, Version 3. Published online June 29, 2019. Accessed April 7, 2021. https://www.ranzcr.com/documents/2836-medical-imaging-consent-guidelines/file
- Lefort LA. Statement from Canadian Medical Protective Association in Relation to Informed Consent in COVID-19 Environment. Published online April 20, 2020. Accessed April 7, 2021. https://car.ca/wp-content/uploads/2020/04/Statement-from-CMPA_-in-Relation-to-Informed-Consent-in-COVID_FINAL.pdf
- Ray JG, Vermeulen MJ, Bharatha A, Montanera WJ, Park AL. Association Between MRI Exposure During Pregnancy and Fetal and Childhood Outcomes. JAMA. 2016;316(9):952. doi:10.1001/jama.2016.12126
- ACR Committee on Drugs and Contrast Media. ACR Manual On Contrast Media. Published online 2020. https://www.acr.org/Clinical-Resources/Contrast-Manual
- Committee Opinion No. 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation. Obstet Gynecol. 2017;130(4):e210-e216. doi:10.1097/AOG.0000000000002355
- Committee Opinion No. 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation: Correction. Obstet Gynecol. 2018;132(3):786. doi:10.1097/AOG.0000000000002858
- Bird ST, Gelperin K, Sahin L, et al. First-Trimester Exposure to Gadolinium-based Contrast Agents: A Utilization Study of 4.6 Million U.S. Pregnancies. Radiology. 2019;293(1):193-200. doi:10.1148/radiol.2019190563
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