The concepts of implantation and biochemical bleeding are two different things. First of all, we have to clarify that the concept of implantation refers to the fertilization of the egg to form a fertilized egg after ovulation, and this fertilized egg is called implantation after it enters the uterine lining. If the embryo is implanted, the HCG in the blood is elevated. Biochemical bleeding refers to the fact that after implantation, the fertilized egg did not successfully implant into the endometrium, there are some abnormalities, implantation failure or embryo apoptosis. At this time, blood tests are often performed, and HCG is once elevated, but then gradually decreases. Clinically, there is vaginal bleeding after menopause, so biochemical bleeding is also called biochemical pregnancy, is a kind of spontaneous abortion process, and implantation is a different matter.