X-Ray Exposure During Pregnancy: Risks, Shielding & Alternatives

Ionizing radiation (X-ray, CT, fluoroscopy) poses fetal risk proportional to dose and gestational age. Most diagnostic exams are well below threat threshold with proper justification.

Radiation Dose & Fetal Risk

Exam	Fetal Dose (mGy)	Risk Context
Chest X-ray (AP)	<0.01	Negligible
Abdominal X-ray	0.1–1.5	Very low
Pelvic X-ray	0.5–3	Low
CT Abdomen/Pelvis	10–50	Concern >50 mGy
CT Pelvis (low-dose)	3–10	Low-moderate

Gestational Age Sensitivity

• Pre-implantation (0–2 wks): All-or-none (miscarriage or no effect). No malformations.
• Organogenesis (3–8 wks): Highest teratogen sensitivity. Threshold ~100–200 mGy for malformations.
• Fetal period (>8 wks): CNS development (8–25 wks most vulnerable). Threshold ~100 mGy for IQ reduction; >500 mGy for microcephaly.
• Carcinogenesis: Linear no-threshold model. ~1 excess cancer/10,000 per 10 mGy (ICRP). Background childhood cancer ~1/500.

Practical Guidelines

1. Justify: Is it necessary? Can US/MRI replace it?
2. Optimize: Lowest dose protocol (ALARA). Collimation, pulsed fluoro, iterative reconstruction (CT).
3. Shield: Lead apron over uterus (if not in beam path). Thyroid shield.
4. Document: LMP, estimated dose, justification in chart.
5. Counsel: Quantify risk. "This chest X-ray = 1 day background radiation."

Safe Alternatives

• Ultrasound: No radiation. First-line for abdomen/pelvis, fetal anatomy, DVT, biliary, appendix (peds).
• MRI: No ionizing radiation. Safe all trimesters (avoid gadolinium unless critical). Best for CNS, soft tissue, placenta.

Accidental Exposure

If pregnant patient receives CT abdomen (20 mGy) at 10 wks: Risk of malformation <1% (baseline 3%). Counsel, document, continue prenatal care. No indication for termination based on radiation alone.

Resources: ACR–SPR Practice Parameter; ICRP Publication 84; ACOG Committee Opinion 823.