Background. Bedside sonography performed by emergency physicians is frequently utilized for real-time clinical decision-making in the emergency department (ED) setting. This includes the sonographic evaluation of pain or bleeding in the first trimester of pregnancy. The detection of intrauterine pregnancy (IUP) or life-threatening conditions, including ectopic pregnancy, is critical. Objectives. This paper will review several important pearls and avoidable pitfalls of this diagnostic modality by brief presentation of illustrative cases followed by discussion of key principles. Case Reports. Three patients evaluated in the ED for bleeding or pain occurring during the first trimester of pregnancy will be presented. Conclusions. When conducting emergency bedside ultrasound for the evaluation of first trimester pregnancy, it is important to avoid common pitfalls that can place your patient at risk. 1. Introduction In recent years, studies have demonstrated that emergency physicians (EPs) can competently perform focused bedside sonography for the evaluation of first trimester pregnancy in the emergency department (ED) [1, 2]. Indeed, EP utilization of ultrasound in first trimester pregnancy is becoming increasingly more common and accepted within emergency care. The American College of Emergency Physicians (ACEP) lists emergency ultrasound in pregnancy as a core area of ultrasound proficiency for the emergency medicine (EM) specialist. In addition, all EM residents are now required to become facile with bedside ultrasound [3]. The detection of potentially life-threatening problems in early pregnancy, particularly ectopic pregnancy, is a fundamental skill [4, 5]. Given the widespread use of this modality, we seek to point out several important and avoidable pitfalls in bedside sonography for first trimester pregnancy through use of representative cases. Important pearls and strategies to avoid these pitfalls are highlighted. 2. Case Presentations 2.1. Case 1: βhCG Level below the Discriminatory Zone A 27-year-old female, Gravida 2, Para 1, presented to the ED following delivery by cesarean section four months priorly, with absence of menstruation since the time of delivery. She presented with severe sharp cramping lower abdominal pain of 18-hour duration. Her vital signs were as follows: temperature 37 degrees centigrade, blood pressure 133/84 millimeters of mercury, heart rate of 156 beats per minute, and a normal respiratory rate and room air oxygen saturation. A urine pregnancy test was positive. The serum quantitative beta human chorionic gonadotropin
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