Guidelines for X-ray Use in Pregnancy

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

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
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
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

Ultrasound is the first-line imaging modality for pregnant patients due to its lack of ionizing radiation 5, 3, 6, 1
MRI without contrast is the preferred second-line imaging modality when ultrasound is inadequate or inconclusive 5, 3, 6, 1
Whole-body diffusion-weighted MRI (WB-DWI/MRI) can replace PET/CT for staging and shows no adverse effects to the fetus 3, 6
MRI is generally safe in pregnancy and does not expose the fetus to ionizing radiation 1

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-based contrast agents should be avoided during pregnancy unless absolutely necessary 3, 6, 1, 2
Gadolinium crosses the placenta and has been associated with increased risk of stillbirth, neonatal death, and rheumatologic/inflammatory skin conditions in offspring 5, 7, 2
MRI without gadolinium is preferred throughout pregnancy 6, 1

All women of childbearing age 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
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

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

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

Perform chest X-ray first, then proceed to CTA chest if needed, as the fetal dose remains <0.3 mGy for suspected pulmonary embolism 2
Perform pregnancy testing prior to imaging, then use ultrasound or MRI instead of CT for suspected appendicitis in the first trimester 2
Limit radiologic investigations to sonography and MRI where possible for inflammatory bowel disease 5
Flexible sigmoidoscopy is preferred over colonoscopy with X-ray guidance whenever possible for inflammatory bowel disease 5