Is a CT (Computed Tomography) scan of the abdomen and pelvis without contrast safe for pregnant women?

CT Abdomen/Pelvis Without Contrast in Pregnant Women

CT abdomen and pelvis without contrast should be avoided in pregnant women due to radiation exposure risks to the fetus and should only be performed when the potential benefits far outweigh the risks in life-threatening situations. 1

Radiation Risk Assessment

• Fetal radiation exposure is a primary concern with CT imaging during pregnancy, as it poses potential risks to the developing fetus 2
• While most diagnostic X-ray studies deliver less than 20 mGy to the uterus (below the 50 mGy threshold for detectable adverse fetal outcomes), CT of the abdomen and pelvis directly exposes the fetus to ionizing radiation 2
• The risk-benefit ratio must be carefully considered, with imaging only performed when the medical necessity outweighs potential risks 2, 3

Preferred Imaging Modalities During Pregnancy

• Ultrasound is the first-line imaging modality for pregnant patients due to its lack of ionizing radiation 1
• MRI without contrast is the preferred second-line imaging modality when ultrasound is inadequate or inconclusive 1
• MRI does not expose the embryo or fetus to ionizing radiation and can effectively detect various conditions 1, 4

Specific Clinical Scenarios

• For microhematuria evaluation in pregnancy:

  • Ultrasound is recommended as the initial imaging modality 1
  • The incidence of malignancy is low in pregnant women with microhematuria 1
  • CT is not used as a first-line imaging modality due to radiation exposure risks 1

• For suspected acute pyelonephritis in pregnancy:

  • Ultrasound is the preferred initial imaging modality 1
  • CT abdomen and pelvis is not supported as initial imaging 1

• For suspected adnexal masses in pregnancy:

  • CT pelvis has no role in the initial evaluation and should be avoided due to radiation dose 1
  • Ultrasound followed by MRI without contrast if needed is the appropriate approach 1

When CT May Be Considered

• In life-threatening situations where the benefit outweighs the risk, such as:

  • Major trauma 1, 5
  • Suspected pulmonary embolism 4
  • Cases where timely diagnosis is critical for maternal survival 1, 5

• In a retrospective study of pregnant patients with abdominal pain, CT showed findings explaining the pain in 36% of cases, with some requiring surgical intervention after normal ultrasound findings 1

Contrast Considerations

• Gadolinium-based contrast agents for MRI should be avoided during pregnancy unless absolutely necessary 1
• Iodinated contrast for CT appears relatively safe during pregnancy but should be used with caution 6

Practical Recommendations

• All women of childbearing age should be questioned about pregnancy status before imaging 2
• Proper shielding of the abdomen should be used whenever possible to minimize fetal exposure 2
• The ALARA principle (As Low As Reasonably Achievable) should be followed to minimize radiation exposure 2, 7

In conclusion, while CT abdomen and pelvis without contrast can provide valuable diagnostic information, the radiation exposure risks to the fetus make it unsuitable as a routine imaging modality during pregnancy. Alternative imaging methods such as ultrasound and MRI should be utilized whenever possible, with CT reserved only for life-threatening situations where the benefits clearly outweigh the risks.