Can I get an MRI (Magnetic Resonance Imaging) brain and MRA (Magnetic Resonance Angiography) brain and neck with contrast when pregnant?

MRI Brain and MRA Brain/Neck with Contrast During Pregnancy

MRI brain and MRA brain/neck with contrast should be avoided during pregnancy unless the potential benefit clearly outweighs the unknown risks to the fetus, as gadolinium-based contrast agents (GBCAs) are considered category C drugs with uncertain fetal effects. 1, 2

Safety Considerations for MRI During Pregnancy

Non-contrast MRI

• MRI without contrast is generally considered safe during pregnancy as it uses non-ionizing radiation
• No known adverse effects on human fetuses have been documented when performed in 1.5T or 3.0T magnets 1
• If diagnostic imaging is necessary, MRI without contrast is preferred over CT due to lack of ionizing radiation 1

Contrast-Enhanced MRI During Pregnancy

Risks of Gadolinium Use

• GBCAs cross the human placenta and result in fetal exposure and gadolinium retention 2
• The American College of Radiology states that gadolinium-based contrast agents should only be used if:
  • The indication is considered critical
  • The potential benefits justify the unknown risk to the fetus
  • Imaging is essential and cannot be delayed 1, 2
• Gadolinium administered to pregnant animals results in measurable gadolinium concentration in offspring tissues for at least 7 months 2

Evidence on Safety

• Human data on the association between GBCAs and adverse fetal outcomes are limited and inconclusive 2
• A retrospective cohort study reported a higher occurrence of stillbirths and neonatal deaths in pregnant women who had GBCA MRI compared to those who did not have an MRI, though this study had limitations 2
• A 2023 literature review found no definitive evidence that GBCAs are harmful during pregnancy, but emphasized that safety remains uncertain 3

Clinical Decision Algorithm

1. First, consider non-contrast alternatives:

   • Ultrasound (safest option during pregnancy) 1
   • MRI without contrast (when ultrasound is inconclusive) 1

2. If contrast is being considered:

   • Determine if the diagnostic information is essential for maternal/fetal health
   • Assess whether imaging can be safely delayed until after pregnancy
   • Evaluate if non-contrast MRI would provide sufficient diagnostic information

3. If contrast is deemed necessary:

   • Document clear rationale for GBCA use during pregnancy
   • Obtain informed consent after discussing unknown risks with patient 1
   • Use the lowest effective dose of gadolinium
   • Consider timing - most inadvertent GBCA exposures occur during the first trimester before pregnancy is recognized 4

Important Caveats

• Approximately 0.12% of pregnancies involve exposure to GBCAs, with 70.2% of these exposures occurring during the first trimester 4
• Small amounts of gadolinium can remain in the body for months to years, with unknown long-term effects 5
• The FDA drug labeling for gadoterate meglumine states: "Because of the potential risks of gadolinium to the fetus, use Gadoterate Meglumine Injection only if imaging is essential during pregnancy and cannot be delayed" 2

Practical Recommendations

• If MRI with contrast is absolutely necessary, ensure proper positioning (left lateral position or with left pelvic tilt) to avoid compression of the inferior vena cava 1
• Consider fetal monitoring before and after the procedure in consultation with an obstetrician 1
• If sedation is required, meperidine or fentanyl are considered safer options, using the lowest effective dose 1

In conclusion, while MRI without contrast is generally considered safe during pregnancy, the use of gadolinium-based contrast agents should be limited to situations where the potential benefits clearly outweigh the unknown risks to the fetus.