not exposed to radiation, approximately 50% of all conceptions are not viable and are spontaneously lost [27]. This is exhibited typically as a late or missed menstrual period, and the woman might not have known that she was pregnant. There is no recommended medical intervention for this situation. Medical advice to the woman should be to seek standard obstetrical care. C. Radiation Exposure Between 2 Weeks and 15 Weeks Postconception At this period, the risk to the conceptus should be evaluated based on the imaged body part/s and the delivered dose. 1. Radiologic procedures outside the abdomen/pelvis PRACTICE PARAMETER 10 Pregnant or Potentially Pregnant Patients For diagnostic radiologic procedures outside the abdomen/pelvis, including the head and neck, the chest, and extremities, the only radiation to which the conceptus is exposed is scattered radiation, which characteristically results in a very low dose. Only under unusual circumstances does the conceptus incur significant radiation exposure. When standard precautions are taken to avoid direct irradiation of the abdomen/pelvis through the use of patient positioning and x-ray beam collimation, the dose delivered does not pose significant risk to the conceptus. 2. Radiologic procedures of the abdomen/pelvis For typical radiologic examinations of the abdomen and/or pelvis, the dose to the conceptus is usually well below any threshold that may induce developmental abnormalities. The only potential risk might be a slight increase in the risk for cancer later in life. Such a risk is very small and under normal circumstances would not justify any medical intervention. Most radiographic examinations deliver much less than 20 mGy to a conceptus. A dose of 20 mGy represents an additional projected lifetime risk of about 40 additional cancers or less per 5,000 babies, or about 0.8%. In other words, there is above 99% likelihood the conceptus will be unaffected by the radiation. For diagnostic fluoroscopy of the abdomen/pelvis, doses may be more substantial, but are not likely to exceed the threshold for induced malformation (more than 100 mGy) in all but exceptional cases. Evaluation of the absorbed dose by a Qualified Medical Physicist, and assessment of the risk based on absorbed dose and gestational age is recommended before definitive discussion with the patient. CT studies can confer significant radiation exposure. Currently, the conceptus dose under well-managed conditions for a single-phase study of the abdomen/pelvis would be less than 35 mGy and typically about 10 to 25 mGy. This low level of exposure would not warrant interruption of pregnancy. Verification of the dose level by a Qualified Medical Physicist is appropriate. For women with pregnancies between 2 and 15 weeks postconception who underwent multiple abdominal and pelvic CT examinations that directly exposed the conceptus, a radiation dose evaluation by a Qualified Medical Physicist is recommended before definitive counseling of the patient. For doses under 100 mGy, there are no identifiable induced developmental defects, and interruption of pregnancy is not warranted based on radiation effects [28]. At doses above 100 mGy, there is a low risk for developmental deficits (eg, gross malformations, growth retardation, mental retardation, small head size). Radiation levels in excess of 150 to 200 mGy carry higher and more significant risk of developmental malformations [4,28]. Any medical consideration of intervention would be based on additional factors associated with the pregnancy. Situations that cumulatively lead to high doses (more than 100 mGy) are very rare and likely entail maternal medical circumstances that further complicate or are complicated by the pregnancy. In these cases, a Qualified Medical Physicist should conduct a radiation dose evaluation. The overall medical picture includes an assessment of other risks associated with normal pregnancies as well as risks specifically associated with the genetic background of the parents and specific medical issues of the pregnant patient. Counseling should take into account all factors of the individual patient’s circumstances, including medical, social, and personal factors. 3. Nuclear Medicine and PET procedures The estimated radiation exposure to the conceptus from the vast majority of diagnostic NM/PET examinations is well below 20 mGy, and thus the likelihood of deterministic effects from such examinations is extremely small. However, a conceptus dose estimate should be provided in all such unanticipated events to educate and reassure all stakeholders (including the radiologist, referring PRACTICE PARAMETER 11 Pregnant or Potentially Pregnant Patients physician, and patient) of the very small risk. (In addition, calculation of such estimates will help identify rare instances whereby a procedure might pose a risk if performed using the standard amount of injected activity.) Dose estimates should also be provided for hybrid (PET/CT and SPECT/CT) examinations [15,18,29-32]. D. Radiation Exposure at More Than 15 Weeks Postconception Potential risks to the developing central nervous system for fetuses that are more than 15 weeks postconception exist only at high doses (eg, more than 200 mGy), well beyond those commonly delivered in multiple radiological or nuclear medicine and PET examinations. During this period, the only potential risk to the fetus from diagnostic doses of radiation is induced cancer. The cancer risk from well-managed radiologic or nuclear medicine and PET procedures is too small to warrant any medical intervention. The lifetime attributed cancer incidence for a fetal dose of 50 mGy in this gestational period is roughly estimated at 2%, but an accurate quantification is impossible [28,33]. Conversely there is about a 98% likelihood the child will be unaffected by the radiation. Most diagnostic examinations result in much lower doses to the fetus. Abdominal/pelvic CT imaging or FDG PET/CT examinations are some of the higher-dose examinations, typically delivering 10 to 35 mGy. VI. DOCUMENTATION Reporting should be in accordance with the ACR Practice Parameter for Communication of Diagnostic