A biochemical pregnancy is one in which the presence of a gestational sac is not detected by ultrasound, but the patient is pregnant and has a miscarriage by biochemical tests. If the HCG drops very slowly after a biochemical pregnancy, there are three main possibilities to consider. First, it is possible that the patient does not have a biochemical pregnancy, but only an ectopic pregnancy with a poorly activated gestational sac, resulting in a very slow decline, a situation that requires continued observation. If it is determined to be an ectopic pregnancy, then conservative treatment or surgery needs to be chosen depending on the situation. Second, it is important to consider the possibility of residual uterine cavity. Patients are advised to go back to the hospital for gynecological ultrasound and blood chorionic gonadotropin examination about 7-10 days after the abortion. Third, the possibility of trophoblastic disease should be considered. In this case, it is necessary to continue to observe the changes in blood HCG, which may rise during the slow decline of blood HCG.