Embryo implantation usually does not have any obvious precursors. Embryo implantation begins with fertilization, when the fertilized egg forms semen that enters the vagina and then the sperm enters the lumen of the fallopian tube. It takes about 7 hours for the egg to meet the energized sperm in the fallopian tube. The process of implantation of the embryo into the uterine lining 6-7 days after fertilization is called implantation. Embryo implantation does not usually cause any uncomfortable symptoms in women, so there are no obvious precursors, but a very small percentage of people may experience bleeding on implantation, mostly due to irritation of the uterine lining during implantation of the fertilized egg, causing a small amount of bleeding on implantation, which usually does not require intervention. When you feel abnormal embryo implantation, you should go to a professional hospital in time to take targeted treatment.