Vaginal bleeding is not uncommon in the first trimester of pregnancy. Ultrasound is the foremost modality for evaluating normal development of the gestational sac and embryo and for discriminating the causes of bleeding. While correlation with quantitative βHCG and clinical presentation is essential, sonographic criteria permit diagnosis of failed pregnancies, ectopic pregnancy, gestational trophoblastic disease and spontaneous abortion. The American College of Radiology Appropriateness Criteria guidelines have been updated to incorporate recent data. A failed pregnancy may be diagnosed when there is absence of cardiac activity in an embryo exceeding 7 mm in crown rump length or absence of an embryo when the mean sac diameter exceeds 25 mm. In a stable patient with no intrauterine pregnancy and normal adnexae, close monitoring is advised. The diagnosis of ectopic pregnancy should be based on positive findings rather than on the absence of an intrauterine sac above a threshold level of βHCG. Following abortion, ultrasound can discriminate retained products of conception from clot and arteriovenous fistulae. The American College of Radiology Appropriateness Criteria® are evidence-based guidelines for specific clinical conditions that are reviewed every two years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.