Another study of female trauma patients reported that 2.9% were pregnant and that the unidentified pregnancy rate was 0.3% [8]. The purpose of screening patients for the possibility of pregnancy is to reasonably minimize radiation exposure to pregnant patients. It should be realized that no screening policy will guarantee 100% detection. In every case, the effort needed to identify unsuspected pregnancy should be weighed against the risk of not detecting a pregnancy. Therefore, different screening policies might apply for high-dose versus low-dose procedures. The vast majority PRACTICE PARAMETER 4 Pregnant or Potentially Pregnant Patients of routine diagnostic studies (including nuclear medicine studies) typically deliver far less than 20 mGy to the uterus. However, some procedures, such as fluoroscopically guided interventional procedures of the pelvic area, may deliver doses above the teratogenic threshold (~100 mGy). In these cases, a stricter method of screening for pregnancy should be applied. A. Determining Pregnancy Status Verification of pregnancy status is not necessary for many common imaging procedures. In certain situations, however, pregnancy status is a fundamental part of the clinical history that should be obtained before performing ionizing imaging studies that may expose the conceptus. Patients may be unaware of their status in the case of early pregnancy. So, laboratory pregnancy testing may be used to determine a patient’s pregnancy status. 1. Examinations That Do Not Require Verification of Pregnancy Status In general, x-ray–based examinations that do not directly expose the pelvis or gravid uterus to the x-ray beam do not require verification of pregnancy status. Such studies include, but are not limited to: a. Chest radiography b. Extremity radiography. c. Any diagnostic examination of the head or neck. d. Mammography e. Any CT imaging outside of the abdomen or pelvis (with the possible exception of the hip) Chest radiography in the third trimester is likely to expose part of the fetus to the direct x-ray beam, but this too can proceed when justified and when optimized ( appropriate technique is used) because the dose to the fetus remains very low and the fetus is less radiosensitive than in early pregnancy. An example of optimization might be to limit the chest radiographic examination to the frontal view and not perform the lateral view. Mammography can also be performed safely at any time during pregnancy. Radiation exposure to a conceptus from a properly performed screening mammogram is expected to be inconsequential [12]. Thus, decisions as to whether to proceed with the examination should be based on clinical circumstances, not radiation risk [13]. For these examinations, although not necessary, facilities may choose to use additional shielding for women of childbearing age as long as the shields do not obscure anatomy necessary for the diagnosis. 2. Examinations That May Require Verification of Pregnancy Status a. Interventional fluoroscopic procedures of the abdomen or pelvis b. Diagnostic angiography of the abdomen or pelvis c. Hysterosalpingography [14] d. Standard-dose CT protocols of the abdomen or pelvis e. Diagnostic Nuclear Medicine PET/CT Determination of pregnancy status has 2 components: clinical history and pregnancy testing. In some circumstances, the clinical history may be sufficient and pregnancy testing is not needed. For example, it may be sufficient for women who attest they cannot reasonably be pregnant and are between regular menstrual periods (eg, has not missed her period), or on long-term birth control, including, but not limited to, hysterectomy or tubal ligation, ongoing oncologic therapy, etc. If clinical history is not sufficient and a woman possibly could be pregnant, then pregnancy testing may be required to determine pregnancy status. In the case of diagnostic nuclear medicine, all radiopharmaceuticals used for diagnostic purposes (except potentially Iodine-131) have short half-lives (ranging from 68 minutes to 78 hours) and low administered activities that result in low radiation doses that pose extremely low radiation risks (Table 2). In this case, a clinical history that the patient cannot reasonably be pregnant is sufficient. For these diagnostic nuclear medicine PRACTICE PARAMETER 5 Pregnant or Potentially Pregnant Patients examinations, pregnancy tests are not routinely required, except for patients whose clinical history is insufficient (eg, they are unsure of their pregnancy status). One exception would be for longer half-life radionuclides that will expose the fetus to >0.50 mGy [15-17]. For diagnostic nuclear medicine studies, this threshold could be attained when using Iodine-131 whole-body imaging for thyroid cancer (usually a 2 to 5 mCi administered activity). In this case, nuclear medicine laboratories may require pregnancy testing in addition to the clinical history to verify pregnancy status. Note: Iodine-123 has a low energy and short half-life, so pregnancy tests are not routinely required for Iodine-123 whole-body scans. In many cases, especially with inpatients, pregnancy history is often available in the medical record. In some facilities pregnancy status must be documented before an order for radiological or nuclear medicine examination is accepted. While this information is helpful in screening for pregnant patients, it should not be the sole record of pregnancy status for women in whom pregnancy has not been diagnosed. Additional assessment of the reproductive status just prior to an examination will help decrease the likelihood of imaging patients with an unsuspected pregnancy. When possible, an interactive electronic order entry system should embed a query about pregnancy status when ordering imaging studies that include the abdomen and/or pelvis of an adolescent girl or woman of childbearing age. Table 2: Examples of diagnostic nuclear medicine examinations that do NOT require routine pregnancy testing prior to radiopharmaceutical administration Radiopharmaceutical Type of scan Single Photon Emitters 99mTc-DTPA Renal scan, Ventilation, Gastric