In vitro frozen embryo transfer requires 2 to 4 days of preparation. Frozen embryo transfer is to prepare the uterine lining, followed by superovulation, then in vitro fertilization, then embryo cultivation to obtain high-quality embryos, and then freezing. The following preparations are needed before IVF frozen embryo transfer: 1. Endometrial preparation: you can choose a natural cycle to determine whether the transfer is necessary by observing ovulation, endometrial thickness and shape. 2. Ovulation promotion: if ovulation is not effective, ovulation promotion can be used, and drugs can be used to promote the development of follicles. After the procedure, if the condition of the uterine lining meets the requirements, embryo freezing and transfer can be carried out. If you want to have a frozen embryo transfer, you can go to the fertility center 2~4 days after your period and follow the doctor’s requirements to prepare the endometrium and prepare the embryo transfer.