Book excerpt: The editors address the anxiety-provoking, but not uncommon, scenario of a woman learning that she is pregnant after diagnostic or therapeutic radiologic exposure, or alternately, requiring X-rays, magnetic resonance, radioisotopes, or ultrasound after she becomes pregnant. Considerations span: the mechanisms for injury by diagnostic radiations, the units and measures of radiation, the amount of radiation absorbed by the conceptus, prenatal risk assessment, clinical management, and case reports (of diseases and traumatic injuries) exemplifying decision recommendations and counseling. Appendixes guide conceptus dose calculations for X-ray exams and radionuclide studies, and list half-lives of 23 radionuclides used in nuclear medicine (5,730 years for Carbon-14). Annotation copyrighted by Book News, Inc., Portland, OR