Ionizing radiation is the kind of electromagnetic radiation produced by unstable atoms (radionuclides) and by machines used in radiology or radiation oncology. The unborn child might be exposed to radiation during diagnostic or therapeutic procedures when a pregnant woman has x rays, fluoroscopy, radiation therapy or is administered liquid radioactive materials. To determine the risks of a radiation exposure for the unborn child, it is best to request specific information regarding the exam(s) from your physician and then consult with a health or medical physicist who works at or consults for the organization where the procedure will be or was performed.
In many instances, especially for routine diagnostic x-ray exams, an evaluation of the radiation exposure is not necessary because the radiological exam will not or did not expose the developing unborn child to harmful amounts of radiation. Routine diagnostic procedures (chest x ray, foot x ray, abdominal x ray, lung CT scan, etc.) expose the unborn child to well less than 5 rem. This level of radiation exposure will not increase risks of birth defects or miscarriage.
However, some therapeutic and interventional radiological procedures may result in higher exposures (this might be radiation therapy of the pelvis for a cancer using a linear accelerator). According to published information, the reported dose of radiation necessary to result in an increased incidence of birth defects or miscarriage is above 10-20 rem. Generally, for the unborn child to receive this high a radiation dose from a medical procedure, the procedure will need to be some form of high-dose radiation therapy in the abdominal area for disease treatment.