Bleeding from implantation does not usually occur on day 5 after intercourse. After intercourse, sperm and egg combine in the fallopian tube to form a fertilized egg, with fertilization occurring mostly within a few hours after ovulation, usually no more than 24 hours. It is about 6-7 days after fertilization that the embryo implants into the uterine lining for implantation. So on day 5 after intercourse the fertilized egg has not yet begun to implant and will not bleed on implantation. Bleeding on the 5th day after intercourse may be caused by luteal insufficiency and decreased estrogen and progesterone levels, or vaginal bleeding due to the presence of cervical diseases such as cervical polyps and cervical lesions. If the bleeding time is short and the amount of bleeding is small, it can be temporarily observed. If the amount of bleeding is large and the bleeding time is long, the patient needs to be examined in time to clarify the cause and target treatment.