Is a computed tomography (CT) scan of the neck with contrast media safe during the first trimester of pregnancy?

CT Neck with Contrast in First Trimester of Pregnancy

CT of the neck with iodinated contrast can be performed during the first trimester of pregnancy when the diagnostic information is essential for maternal care and the benefit outweighs the potential risks, but it should only be used when ultrasound or non-contrast MRI cannot provide adequate diagnostic information. 1, 2

Radiation Safety Considerations

• The neck CT delivers negligible radiation exposure to the fetus, as the primary beam is directed away from the abdomen and pelvis where the developing embryo is located. 3
• Fetal radiation doses below 50 mGy are not associated with detectable increases in adverse fetal outcomes including malformations, growth restriction, or fetal death. 1, 3
• The currently accepted cumulative dose of ionizing radiation to the fetus is less than 50 mGy throughout pregnancy. 1
• Head and neck CT imaging delivers minimal scatter radiation to the fetus, well below concerning thresholds. 3

Iodinated Contrast Agent Safety

• Iodinated contrast agents are generally considered safe during pregnancy, including the first trimester, and should be used when clinically necessary for essential diagnostic information. 2, 4
• The American College of Radiology recommends that IV iodinated contrast can be administered during the first trimester when the potential benefit outweighs the risk. 2
• Modern non-ionic iodinated contrast agents have no effect on the thyroid gland, though theoretical risk of neonatal hypothyroidism exists. 1, 3
• Less than 0.01% of CT contrast appears in breast milk, making breastfeeding safe after administration. 1, 3

Clinical Decision-Making Algorithm

When neck CT with contrast is being considered in the first trimester:

1. Document the clinical indication and confirm that the diagnostic information is essential for maternal care and cannot be obtained by safer alternatives. 2, 3

2. Consider ultrasound first as the preferred imaging modality throughout pregnancy when applicable. 1

3. Consider non-contrast MRI as second-line when ultrasound is inadequate, as MRI without gadolinium is considered safe in all trimesters. 1, 5

4. Reserve CT with contrast for situations where ultrasound and MRI cannot provide adequate diagnostic information and the clinical situation requires urgent or definitive diagnosis. 3

5. Obtain informed consent after discussing risks and benefits with the patient. 2

Important Caveats

• Gadolinium-based MRI contrast should be avoided during the first trimester unless absolutely essential to maternal or fetal health, as gadolinium crosses the placenta, accumulates in fetal tissues and amniotic fluid, and has been associated with increased risk of rheumatologic conditions in offspring and potential increased risk of stillbirth or neonatal death. 2, 5, 4

• Iodinated contrast is safer than gadolinium if contrast-enhanced imaging is required. 3, 6

• In acute neurological or life-threatening maternal conditions, CT should not be withheld or delayed due to exaggerated concern about radiation, as the maternal benefit of accurate diagnosis outweighs the minimal fetal risk. 6