Answer to Question #11549 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I perform computed tomography (CT) scans in a hospital. A few days ago, I performed a CT scan on a woman's pelvis. The protocol used for this examination results in a dose to the patient between 10 and 15 milligray (mGy).
At the time of the CT scan, I did not know the patient was four weeks pregnant. Now I feel great guilt. Please tell me frankly if there will be an effect on the fetus.
With a dose that small and at just four weeks into the pregnancy, the risk for harmful effects is low.
We believe the most sensitive period of a pregnancy for possible harmful effects to the fetus from radiation is at 8–15 weeks with radiation doses above 50 mGy. Below this radiation dose, while there may be some increased risk, the natural background risk of birth defects (3% of births) and miscarriage (15% of births) far exceed any risk from the radiation exposure.
The Health Physics Society's fact sheet on "Radiation Exposure and Pregnancy" might be a good resource for you: http://hps.org/documents/pregnancy_fact_sheet.pdf.
From what we know about the risk of radiation exposure to a developing fetus, it is unlikely the radiation dose from the CT scan caused any harmful effects.
Certified Medical Health Physicist