Is MRI (Magnetic Resonance Imaging) with contrast safe during pregnancy?

From the Guidelines

MRI with contrast should not be used during pregnancy unless absolutely necessary, as the potential benefits must clearly outweigh the potential risks to the fetus. The contrast agent used in MRI, typically gadolinium-based contrast agents (GBCAs), can cross the placenta and enter the fetal circulation, raising theoretical concerns about potential harm to the developing fetus 1. While no definitive human studies have shown adverse effects, animal studies have revealed adverse effects, and the FDA has classified GBCAs as category C drugs, indicating that their use in pregnancy is restricted to situations where the potential benefits far outweigh the potential risk to the fetus 1.

Key Considerations

• Non-contrast MRI is considered safe and is preferred for pregnant women who require diagnostic imaging 1.
• Other modalities like ultrasound should be considered first for pregnant women who require diagnostic imaging 1.
• The American College of Radiology advises that GBCAs should be used during pregnancy only when the potential benefits justify the potential unknown risks to the fetus 1.
• If MRI with contrast is deemed essential for diagnosis, the benefits must clearly outweigh the potential risks, and this decision should be made jointly between the patient and healthcare providers 1.

Recommendations

• Pregnant women who require diagnostic imaging should discuss their specific situation with their obstetrician and radiologist to determine the most appropriate approach for their individual circumstances 1.
• Informed consent should be obtained from the patient after discussion with the referring physician if MRI with contrast is deemed necessary 1.
• The use of GBCAs during pregnancy should be diligently documented, and the rationale for their use should be clearly stated 1.

From the FDA Drug Label

GBCAs cross the placenta and result in fetal exposure and gadolinium retention. The human data on the association between GBCAs and adverse fetal outcomes are limited and inconclusive... Because of the potential risks of gadolinium to the fetus, use gadobutrol injection only if imaging is essential during pregnancy and cannot be delayed.

GBCAs administered to pregnant non-human primates (0. 1 mmol/kg on gestational days 85 and 135) result in measurable gadolinium concentration in the offspring in bone, brain, skin, liver, kidney, and spleen for at least 7 months

MRI with contrast is not entirely safe during pregnancy. The FDA drug labels for gadobutrol 2 and gadoterate meglumine 3 indicate that:

• Gadolinium-based contrast agents (GBCAs) cross the placenta, resulting in fetal exposure and retention.
• Human data is limited and inconclusive, making it difficult to determine the potential risks of GBCAs to the fetus.
• Animal studies have shown embryolethality and retardation of embryonal development at high doses.
• Use of GBCAs during pregnancy should be limited to essential imaging that cannot be delayed.

From the Research

MRI with Contrast during Pregnancy

• The use of MRI with contrast during pregnancy is a topic of concern, with various studies examining its safety [(4,5,6,7,8)].
• Noncontrast MRI is generally considered safe in pregnancy, as no evidence of fetal adverse effects has been demonstrated to date 4.
• However, the use of gadolinium-based contrast agents is a concern, as they can accumulate in the amniotic fluid and fetal tissue [(4,6)].
• Some studies suggest that iodinated CT contrast agents may be safer than gadolinium-based MRI contrast agents 4.
• The safety of gadolinium-based contrast agents during pregnancy, particularly during the first trimester, remains uncertain, and more large-scale, long-term studies are needed to clarify their safety 6.

Risks and Benefits

• The risks of MRI with contrast during pregnancy must be weighed against the benefits, and alternative imaging modalities, such as non-contrast MRI or ultrasound, should be considered when necessary [(5,6,7,8)].
• Exposure to gadolinium-based contrast agents and sedation for MRI during pregnancy should be avoided whenever feasible 5.
• Healthcare providers should carefully evaluate the benefits and risks of using contrast agents during pregnancy and consider alternative imaging modalities [(6,7,8)].

Guidelines and Recommendations

• Guidelines for the use of CT, MRI, and contrast media during pregnancy have been developed, emphasizing the importance of evidence-based decision-making and careful consideration of the risks and benefits 7.
• The use of contrast media during pregnancy should be justified by a clear clinical indication, and the smallest possible dose should be administered 8.
• After parental administration of an iodinated contrast medium, the neonate's thyroidal function should be checked during the first week after birth 8.