In the case of ectopic pregnancy, the change of serum HCG will not have a significant doubling compared to intrauterine pregnancy. When the value of HCG reaches a certain level, it will fluctuate above and below this value, and at this time, through the ultrasound test, through the change of HCG, the corresponding diagnosis of intrauterine pregnancy or ectopic pregnancy will be made accordingly. Sometimes in the case of ectopic pregnancy, the value of HCG is relatively low, and it is not possible to exclude or clarify the existence of ectopic pregnancy by simple monitoring of HCG. Depending on the HCG variation or the specific range of values, the ultrasound may guide the subsequent treatment, either conservative observation, conservative medication, emergency surgery and laparotomy.