In vitro transfer is usually performed 3-5 days after egg retrieval, which corresponds to the normal menstrual cycle, where ovulation usually occurs in the middle of the menstrual cycle. However, in some patients with irregular menstrual cycles or with slow follicular growth, transplantation may take place later in the corresponding menstrual period. In some cases, the follicles grow very fast and the menstrual cycle is relatively short, so the transfer will take place before the 14th day of the menstrual cycle. Therefore, it is normal to transfer IVF embryos around the 14th day of the cycle, but in some cases it may be less than 14 days or even more than 14 days for special patients.