Physicians diagnose ectopic pregnancy (EP) primarily through serum human chorionic gonadotropin (hCG) values, vaginal ultrasound findings, and medical history. Clinical judgment and serum assays, which are essential to prevent misdiagnosis of ectopic pregnancy. A recent researcher evaluated the accuracy of serum hCG assays to predict the outcome of ectopic pregnancy. Researchers followed 1005 women until they were diagnosed with ectopic pregnancy (179), miscarriage (567), or intrauterine pregnancy. The women, from three locations in the United States, all complained of pain or bleeding in early pregnancy and had ultrasound suggestive of an unknown pregnancy location. Intrauterine pregnancy was assessed by a greater than 35% rise in hCG on more than 2 consecutive days to avoid misdiagnosis. The sensitivity and specificity for predicting EP were highest when the rise in hCG was less than 35% for more than 2 consecutive days and the decline in hCG (compared with the initial hcg level) was 36% to 47% within 2 days. However, ectopic pregnancy and intrauterine pregnancy each have a 16.8% and 7.7% false diagnosis rate using serum hCG alone.