Ectopic pregnancy is a potentially life-threatening outcome of pregnancy that occurs with the implantation of an embryo outside of the endometrial cavity. Classically considered a "must not miss" diagnosis, ectopic pregnancy is a common emergency department presentation, associated with a symptom triad of amenorrhea, vaginal bleeding, and abdominal pain. However, varied presentations of ectopic pregnancy or lack of typical risk factors can complicate the evaluation and diagnosis of this condition. This case report describes an atypical presentation of ectopic pregnancy after a reported spontaneous abortion, in which the patient was initially discharged with a diagnosis of pelvic inflammatory disease. This case provides an illustration of ectopic pregnancy that presented without classically associated symptoms, and also highlights how anchoring bias and pre-emptive closure, among other cognitive biases, contributed to a missed diagnosis.
