MRI in Pregnant Patients: |
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No consistent or convincing body of evidence has yet been assembled to suggest that short-term exposure to electromagnetic fields (such as the exposure that occurs during MR imaging) harms the developing fetus. The reader should be aware, however, that in a a few studies, prolonged and/or high-intensity exposure to electromagnetic radiation has been linked with some deleterious effects on embryogenesis, chromosomal structure, or fetal development. Such positive studies purport to have demonstrated: accelerated cleavage in sea urchin embryos, lower birth weights in rats, chromosomal aberrations in human lymphocyte cultures, altered bacterial mutation rates, modulation of mitosis frequency in slime molds, and malformations of chick and frog embryos. Nevertheless, far more studies have failed to demonstrate any measurable ill effects of electromagnetic fields on animal or human embryos. Therefore, at present, there is no conclusive scientific evidence to support a direct relationship between MRI exposure and disorders of embryogenesis. Of course, neither has it been proved that small or subtle effects do not occur.
For this reason we do not cavalierly recommend MR imaging in pregnant patients, particularly if there is no overpowering clinical necessity for the scan or if an equivalent non-ionizing diagnostic technique (e.g., ultrasound) will suffice. Notwithstanding these cautions, we do not hesitate to scan a pregnant patient when such a study is medically indicated. Reasonable indications for an MR scan during pregnancy might include herniated disk, possible stroke, or complex suspected fetal abnormality.
Considerable reassurance of MRI safety is provided by the JAMA paper by Ray et al (2016). In this population-based cohort study of more than 1.4 million pregnancies, non-contrast first-trimester MRI was not significantly associated with congenital anomaly, stillbirth, or neonatal death.
Although the direct effects of RF irradiation in MRI may be harmless, localized heating of fetal tissues (caused by RF-induced currents) can indeed result in developmental anomalies (in animals) when the core body temperature is increased by 2-4 ºC. For this reason alone, everything possible should be done to minimize the specific absorption rate (SAR) while imaging a pregnant patient. Such strategies, discussed in another Q&A, include scanning only in "Normal Operating Mode", avoiding high SAR sequences, parallel transmission, and the use of saturation pulses. Additionally, although unproven, exposure of the fetus to loud noises should be avoided through the use of "quiet gradients" or similar acoustic reduction techniques.
When an MRI has been ordered in a pregnant patient, either I or one of my resident physicians talks personally with her to obtain informed consent for imaging. We explain the concepts expressed in the first three paragraphs — that there are no proven harmful effects of MRI on the fetus. . . but the risk may not be zero. We also inform each patient that any alternative radiologic diagnostic tests (such as CT or myelography) would likely require using x-rays, and that the risks of ionizing radiation on the developing fetus is no less, and is probably greater, than the theoretical risks of MRI. In the final analysis, the most important factor in having a healthy baby is having a healthy mother.
Gadolinium in pregnancy should be avoided if at all possible and used only after careful assessment of benefits v risk. This topic is discussed more completely in a dedicated Q&A.
Gadolinium in pregnancy should be avoided if at all possible and used only after careful assessment of benefits v risk. This topic is discussed more completely in a dedicated Q&A.
References
European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). Potential health effects of exposure to electromagnetic fields (EMF). European Commission, 2015. (developmental/reproductive effects discussed on pp 144-153) [DOI link]
IEEE International Committee on Electromagnetic Safety. Expert Reviews. Available at [this link]. (Comprehensive listing of over 90 high quality expert reviews by various consensus panels and government agencies world-wide published between 2010 and 2020.)
RadiologyInfo.org. MRI safety during pregnancy. (RSNA/ACR-sponsored information site for patients with written and video explanations, accessed September 2020)
Ray RG, Vermeulen MJ, Bharatha A, et al. Association between MRI exposure during pregnancy and fetal and childhood outcomes. JAMA J Amer Med Assoc 2016; 316:952-961. (important large scale study showing no significant risk to fetus for first trimester MRI without gadolinium).
SSM’s Scientific Council on Electromagnetic Fields. Report number 2020:04: Recent research on EMF and health risk. (developmental/reproductive effects discussed on pp 28-42). Available at [this link].
Ziskin MC, Morrissey J. Thermal thresholds for teratogenicity, reproduction, and development. Int J Hyperthermia 2011; 27:374-387. [DOI Link]
European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). Potential health effects of exposure to electromagnetic fields (EMF). European Commission, 2015. (developmental/reproductive effects discussed on pp 144-153) [DOI link]
IEEE International Committee on Electromagnetic Safety. Expert Reviews. Available at [this link]. (Comprehensive listing of over 90 high quality expert reviews by various consensus panels and government agencies world-wide published between 2010 and 2020.)
RadiologyInfo.org. MRI safety during pregnancy. (RSNA/ACR-sponsored information site for patients with written and video explanations, accessed September 2020)
Ray RG, Vermeulen MJ, Bharatha A, et al. Association between MRI exposure during pregnancy and fetal and childhood outcomes. JAMA J Amer Med Assoc 2016; 316:952-961. (important large scale study showing no significant risk to fetus for first trimester MRI without gadolinium).
SSM’s Scientific Council on Electromagnetic Fields. Report number 2020:04: Recent research on EMF and health risk. (developmental/reproductive effects discussed on pp 28-42). Available at [this link].
Ziskin MC, Morrissey J. Thermal thresholds for teratogenicity, reproduction, and development. Int J Hyperthermia 2011; 27:374-387. [DOI Link]
Related Questions
Can gadolinium be given to pregnant women?
Does working around the electromagnetic fields of an MRI scanner carry any health risks? Should exposure be limited? What about pregnant techs and staff?
Can gadolinium be given to pregnant women?
Does working around the electromagnetic fields of an MRI scanner carry any health risks? Should exposure be limited? What about pregnant techs and staff?