Frozen embryo on the eighth day to measure the gray mark is getting fainter and fainter may be caused by short time of implantation or embryo implantation failure, can be further clarified under the guidance of the doctor. 1. Short bedtime: Frozen embryo transfer is a method of in vitro fertilization-embryo transfer technology, which should be operated by professional physicians. Generally the eighth day after the frozen embryo transfer may be due to the late implantation of the embryo after the transfer, which makes the gray mark of the test paper more and more faint, can be further judged under the guidance of the doctor combined with the blood HCG level. 2. Failure of embryo implantation: When the embryo implantation fails after frozen embryo transfer, the level of blood HCG produced in the body will be less and less low, which will also make the gray mark more and more faint, and can also be combined with the measurement of blood HCG level under the instruction of the doctor to confirm. When the gray mark is getting fainter and fainter on the eighth day of embryo freezing, it is necessary to review the test under the guidance of the doctor.