The HCG value of ectopic pregnancy is increased because it is secreted by the trophoblast cells after the fertilized egg has been implanted. The HCG level is therefore related to the site of implantation, the growth capacity and the growth status of the egg. If the HCG level is very low, it may not always be ectopic pregnancy, but it may be embryonic arrest or inevitable miscarriage, so a low HCG level does not necessarily mean ectopic pregnancy. The diagnosis of ectopic pregnancy requires an ultrasound examination of the uterus without a gestational sac, a small amount of bleeding with abdominal pain and an increase in HCG value, so it is more correct to treat an increased HCG value clinically after excluding ectopic pregnancy.