Which imaging techniques are not associated with risk in pregnancy?

• A. X-ray
• B. Ultrasound and MRI
• C. CT scan
• D. Nuclear medicine

Answer: (B)

Imaging safety in pregnancy centers on whether the technique uses ionizing radiation. Ultrasound relies on sound waves, not x-rays, so it does not expose the fetus to ionizing radiation and is routinely used in pregnancy with minimal risk when performed by skilled staff. MRI also does not involve ionizing radiation; when used without gadolinium contrast, it is generally considered safe during pregnancy, with gadolinium avoided unless absolutely necessary because of potential fetal risks.

Imaging methods that do involve ionizing radiation carry fetal exposure. X-ray and CT scans deliver ionizing radiation, and even with shielding, there is some fetal dose, with CT typically delivering higher doses. Nuclear medicine uses radiopharmaceuticals that can cross the placenta, so fetal exposure is a concern and these studies are used only when the benefits clearly outweigh the risks and exposure is minimized.

So the modalities without ionizing radiation exposure—ultrasound and MRI—are the ones not associated with fetal radiation risk.