In vitro transfer of frozen embryos after about 7 days of implantation, the time of implantation of frozen embryos is basically the same as the time of implantation of normal fertilized eggs, if the embryos do not implant within 14 days is a suppression failure. The process of implantation is also known as embryo burial in the uterine lining and is a very critical part of the conception process. IVF is a form of assisted reproduction in which sperm and eggs are obtained and then fertilized in a special culture in an in vitro test tube, allowing the sperm and eggs to combine to form a fertilized egg. If the hormone level and the thickness of the endometrium are not suitable for transfer, the embryos need to be frozen and stored in liquid nitrogen, and when the body is ripe for embryo transfer, the frozen embryos will be rewarmed and thawed.