Can a pregnant woman have a computed tomography (CT) scan with contrast?

CT with Contrast During Pregnancy

CT with iodinated contrast is not absolutely contraindicated in pregnancy, but should only be used when the diagnostic information is essential and cannot be obtained through safer alternatives like ultrasound or non-contrast MRI. 1

Imaging Hierarchy in Pregnancy

The preferred approach follows this algorithmic sequence:

• First-line: Ultrasound without contrast is the preferred imaging modality throughout pregnancy 1
• Second-line: MRI without gadolinium is preferred over CT imaging when ultrasound is inadequate 1, 2
• Last resort: CT (with or without contrast) should be reserved for problematic situations where diagnosis cannot be made on ultrasound or MRI 1

When CT with Contrast May Be Justified

Iodinated contrast should only be used if absolutely required to obtain diagnostic information that would affect the care of the fetus or mother. 1 This typically applies to:

• Life-threatening maternal conditions requiring immediate diagnosis (e.g., suspected pulmonary embolism, acute trauma with serious injury) 3
• Situations where ultrasound and MRI have failed to provide adequate diagnostic information 1
• Clinical scenarios where diagnostic delay poses greater risk than radiation exposure 4, 3

Safety Considerations

Radiation Exposure

• CT abdomen/pelvis delivers 13-25 mGy fetal dose 1
• Cumulative ionizing radiation exposure should remain below 50 mGy 1
• When CT is required, always use low-dose protocols 1

Iodinated Contrast Risks

• Modern non-ionic iodinated contrast has no effect on the thyroid gland 1
• Potential risk of neonatal hypothyroidism exists theoretically, but is minimal with current agents 1
• Less than 0.01% of CT contrast appears in breast milk, making breastfeeding safe after administration 1

Critical Pitfalls to Avoid

Do not delay or withhold CT in truly emergent situations due to exaggerated concern about radiation. 4 In acute life-threatening maternal conditions (trauma, suspected pulmonary embolism), the risks of delayed diagnosis typically outweigh imaging risks 4, 3.

Always document the risk-benefit discussion with the patient and the clinical rationale for choosing CT over safer alternatives 4. Direct consultation between the referring clinician and radiologist is essential to determine the most appropriate imaging strategy 4.

Avoid gadolinium-based MRI contrast as an alternative - gadolinium is actually more concerning than iodinated CT contrast because it crosses the placenta, accumulates in amniotic fluid and fetal tissues, and has been associated with increased risk of stillbirth, neonatal death, and rheumatologic conditions in offspring 1, 2, 5.

Practical Algorithm

1. Can ultrasound answer the clinical question? If yes, use ultrasound 1
2. If ultrasound inadequate, can non-contrast MRI provide the answer? If yes, use MRI without gadolinium 1, 2
3. Is the clinical situation life-threatening or will diagnostic delay significantly harm mother or fetus? If yes, proceed with CT 4, 3
4. Is iodinated contrast essential for diagnosis, or will non-contrast CT suffice? Use contrast only if essential 1
5. Use low-dose CT protocols and proper abdominal shielding when possible 1