Considerations for Patients Exposed Between 2 Weeks and 15 Weeks Postconception

For pregnancies that are more than 2 weeks and less than 15 weeks postconception, the dose to the conceptus becomes an especially important factor. 

1. Radiologic procedures outside the abdomen/ pelvis 

For diagnostic radiologic procedures outside the abdomen/pelvis, which includes the head and neck, the chest, and all extremities, the only radiation to which the conceptus is exposed is that of scattered radiation, which characteristically results in a very low dose. For any significant radiation exposure to have occurred there would have to have been some very unusual circumstances. For more typical examinations in which 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 would not pose any significant risk to the conceptus. 

2. Radiologic procedures of the abdomen/pelvis 

For well-managed, common radiologic examinations of or including the pelvis, the dose to the conceptus would be well below any threshold dose necessary to induce developmental abnormalities. The only potential risk might be an increase in the risk for cancer later in life. Such a risk is small and under normal circumstances would not be justification for any medical intervention. For example, due to differences in environmental radiation, pregnant women who live in Denver, Colorado expose their conceptuses to radiation levels measurably greater than those to which the conceptuses of women in coastal cities are exposed (by about 0.6 mSv). Such differences theoretically place the conceptuses of the Denver women at an increased risk of about 1 additional cancer in 5,000 babies. Most radiographic examinations deliver less dosage and usually 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%. To put this into perspective, if out of concern for the increased risk of induced cancer an abortion were recommended for every fetal exposure of 20 mGy, and then more than 99% of such abortions would be of children unaffected by the radiation. For diagnostic fluoroscopy of the abdomen/ pelvis, doses are more substantial, but are not likely to exceed the threshold for induced malformation (more than 100 mGy) in all but exceptional cases. An evaluation of the absorbed dose and assessment of the risk based on absorbed dose and gestational age might be appropriate before definitive discussions with the patient take place. For women who had CT studies, the doses may be substantial. Currently, the dose under wellmanaged conditions for a single-phase study of the abdomen including the pelvis would be less than 50 mGy and typically about 20 to 35 mGy. For standard single-phase abdomen/pelvic CT examinations, the risks posed would not warrant any concern that might prompt medical intervention. Verification of the dose level by a qualified medical physicist is an appropriate consideration. For women with pregnancies between 2 weeks to 15 weeks postconception, who underwent multiple abdominal and pelvic CT examinations that directly expose the conceptus, a radiation dose evaluation by a medical physicist is recommended before definitive counseling of the patient. For doses under 100 mGy, the risks are considered too small to warrant any medical intervention [19] At these doses there are no risks for induced developmental deficits that would be physically identifiable. At doses above 100 mGy the risks for developmental deficits (e.g., gross malformations, growth retardation, mental retardation, small head size) start to appear but remain at a low risk until doses exceed 150-200 mGy [3,19]. Any medical considerations for 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. Any recommendation for intervention in a pregnancy should be determined from the overall medical picture and not just one aspect of that picture. 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 and social conditions of the pregnant patient.