What are the guidelines for using X-rays (X-radiation) in pregnancy?

Guidelines for X-ray Use in Pregnancy

X-rays can be safely performed during pregnancy when clinically indicated, as most diagnostic X-ray procedures deliver fetal radiation doses far below the safety threshold of 50-100 mGy, with the benefits of accurate maternal diagnosis typically outweighing negligible fetal risks. 1, 2

Radiation Safety Thresholds

• Fetal doses below 50 mGy are not associated with detectable increases in adverse fetal outcomes including malformations, growth restriction, or fetal death 1, 2
• The threshold for significant risk of fetal damage is set at 100 mGy 3, 1, 2
• Most diagnostic X-ray studies deliver far less than 20 mGy to the uterus, including single-phase CT studies of the abdomen 1
• Risk of malformations increases only with doses exceeding 150 mGy 2

X-ray Safety by Anatomic Region

Low-Risk Imaging (Proceed Without Hesitation)

• Chest X-ray delivers <0.01 mGy to the fetus—approximately 1/5,000,000th of the safety threshold—and should be performed without hesitation when clinically indicated 4
• Head/neck and extremity radiographs expose the fetus to minimal radiation (<1-10 mGy) and should not be deferred when medically necessary 1, 2
• Simple X-rays with proper abdominal shielding carry negligible fetal radiation exposure of <0.1 mGy 3, 1

Moderate-Risk Imaging (Use With Appropriate Justification)

• Pelvis radiograph delivers approximately 1.1 mGy fetal dose 2
• Single-phase abdominal CT delivers less than 20 mGy 1
• Chest CT delivers approximately 0.3 mGy to the fetus 2, 4

Higher-Risk Imaging (Reserve for Essential Situations)

• CT abdomen/pelvis should be avoided when possible, as it delivers 25-35 mGy fetal dose, but may be performed when the benefit clearly outweighs the risk in life-threatening situations 1, 2
• Abdominal/pelvic imaging with X-rays should be avoided when possible due to direct fetal exposure 1

Preferred Alternative Imaging Modalities

• Ultrasound is the first-line imaging modality for pregnant patients due to its lack of ionizing radiation 3, 1
• MRI without contrast is the preferred second-line imaging modality when ultrasound is inadequate or inconclusive 3, 1
• Whole-body diffusion-weighted MRI (WB-DWI/MRI) can replace PET/CT for staging and shows no adverse effects to the fetus 3
• MRI is generally safe in pregnancy and does not expose the fetus to ionizing radiation 1, 5

Contrast Agent Considerations

Iodinated Contrast (for X-ray/CT)

• Iodinated IV contrast appears safer than gadolinium-based MRI contrast 2
• Modern non-ionic iodinated contrast has minimal theoretical risk of neonatal hypothyroidism 2
• Less than 0.01% of CT contrast appears in breast milk, making breastfeeding safe after administration 2
• Use iodinated contrast only if absolutely required to obtain diagnostic information that would affect care 2

Gadolinium Contrast (for MRI)

• Gadolinium-based contrast agents should be avoided during pregnancy unless absolutely necessary 3, 1, 2
• Gadolinium crosses the placenta and has been associated with increased risk of stillbirth, neonatal death, and rheumatologic/inflammatory skin conditions in offspring 3, 2
• MRI without gadolinium is preferred throughout pregnancy 3, 1

Clinical Decision-Making Framework

Pre-Imaging Assessment

• All women of childbearing age (typically 12-50 years) should be questioned about pregnancy status before imaging 1
• For high-dose procedures like fluoroscopy, pregnancy testing within 72 hours is recommended unless medical urgency prevents it 1
• Document the clinical indication and risk-benefit assessment in the medical record 2, 4

Risk-Benefit Analysis

• The medical necessity of the examination must outweigh potential risks to the fetus 1
• The risk of missing a potentially serious maternal diagnosis far outweighs the negligible radiation risk from most diagnostic X-rays 4
• Delaying or avoiding necessary imaging poses greater risk to both mother and fetus than the radiation exposure itself 4

Radiation Protection Principles

• Follow the ALARA principle (As Low As Reasonably Achievable) to minimize radiation exposure 1
• Use proper shielding of the abdomen whenever possible to minimize fetal exposure 3, 1
• Keep cumulative ionizing radiation exposure below 50 mGy to minimize risk 2
• Use low-dose CT protocols when CT is required 2

Common Pitfalls and Caveats

• Avoid unnecessary anxiety leading to diagnostic delay—counsel patients that most diagnostic X-rays deliver radiation equivalent to a few days of natural background exposure 4
• Modern evidence indicates abdominal shielding for chest X-rays provides no meaningful benefit and may require repeat imaging if positioning is compromised 4
• For chest X-rays, lead shielding applied externally to the pelvis and abdomen will not intercept scattered radiation, as fetal exposure comes from scattered radiation emanating from the directly exposed chest structures 4
• Collimate the field to the area of interest to ensure fetal exposure is minimized 4
• Nuclear medicine procedures using radioactive iodine are contraindicated, as they can cross the placenta and affect the fetal thyroid after 12 weeks gestation 1

Special Clinical Scenarios

Suspected Pulmonary Embolism

• Perform chest X-ray first, then proceed to CTA chest if needed, as the fetal dose remains <0.3 mGy 2

Suspected Appendicitis (First Trimester)

• Perform pregnancy testing prior to imaging, then use ultrasound or MRI instead of CT 2

Trauma Evaluation

• Imaging should be used to evaluate pregnant trauma patients only when the benefits outweigh the risks 5
• Standard trauma protocols may be modified to use ultrasound and MRI when feasible 5

Inflammatory Bowel Disease

• Limit radiologic investigations to sonography and MRI where possible 3
• Flexible sigmoidoscopy is preferred over colonoscopy with X-ray guidance whenever possible 3