Light em up? Radiation use in pregnancy

Diagnostic imaging in pregnancy is usually safer than clinicians and patients fear. ACOG notes that most radiography, CT, and nuclear medicine studies deliver fetal doses far below levels associated with reported fetal harm, while the larger immediate risk in many scenarios is missing the mother's diagnosis.

Radiation Risk in Pregnancy

• ACOG safety benchmark: No reported fetal harms have been documented below 50 mGy, a practical anchor for counseling when medically necessary imaging is on the table.
• Maternal risk perspective: Radiation risk is usually higher for the mother than the fetus, especially because developing breast tissue in pregnancy is more radiosensitive.
• ALARA without paralysis: As low as reasonably achievable still applies, but necessary CT, radiography, or nuclear imaging should not be withheld solely because a patient is pregnant.
• Everyday dose comparison: A standard chest x-ray is in the same ballpark as a transcontinental flight, and many common x-rays expose the fetus to even less radiation.
• Cancer risk framing: Radiation-related cancer risk is real but small; even higher-dose studies like pelvic CT still leave the overwhelming likelihood of no malignant consequence. We walk through a bedside way to say that out loud in the episode.

Practical Imaging and Contrast Decisions

• Shared decision budget: Using a simple radiation budget built around the 50 mGy benchmark can make informed consent clearer and calm anxiety during PE or trauma imaging decisions.
• CT contrast in pregnancy: Iodinated IV contrast crosses the placenta, but human observational data have not shown teratogenicity or clinically important fetal thyroid harm.
• Gadolinium caution: Gadolinium is treated as potentially teratogenic and should be reserved for situations where it meaningfully improves the diagnostic performance of MRI.
• Breastfeeding after contrast: Both CT contrast and gadolinium are considered compatible with breastfeeding because only tiny amounts reach milk and even less is absorbed by the infant.
• Testing over avoidance: The key decision is whether the study is necessary, not whether it is perfectly risk-free; protecting maternal health is often the best way to protect the fetus. We get into the consent language in the chapter.

References:

1. Morgenstern, J. Diagnostic imaging during pregnancy and lactation, First10EM, November 20, 2023. Available at: (Link)
2. Committee Opinion No. 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation. Obstet Gynecol. 2017 Oct;130(4):e210-e216.  Erratum in: Obstet Gynecol. 2018 Sep;132(3):786. PMID: 28937575