If there is bleeding from implantation but pregnancy is not detected, it is considered that the number of days is too short. 5-7 days after intercourse, pregnancy may not be detected by pregnancy test or blood draw, and it is necessary to wait for about 12 days after intercourse to detect the pregnancy. The bleeding may not necessarily be caused by the implantation, but may be caused by contact bleeding during intercourse due to cervical erosion or chronic cervicitis, luteal insufficiency or abnormal ovulation, or endometrial polyps, which may also cause a small amount of bleeding, not necessarily caused by the implantation, and pregnancy cannot be detected without conception either after implantation or 12 days after intercourse. If there is a biochemical pregnancy there will be bleeding from implantation and the HCG will drop to normal soon after a transient increase and may test negative for pregnancy.