After 28 days of down-regulation, transplantation usually occurs around 2-3 weeks. Down-regulation is usually chosen to be injected with long-acting GnRH-a analogs, gonadotropin-releasing hormone agonists, 1-2 days after the onset of menstruation. 28 days after down-regulation, blood draws as well as ultrasound are required to find out if the down-regulation is up to the standard. If the criteria for down-regulation are met, hormone replacement cycle therapy can be performed. Hormone replacement cycle treatment usually starts with estrogen, such as estradiol valerate tablets, and the ultrasound should be repeated after 12 days of using the medication to find out the thickness of the uterine lining. When the endometrial thickness permits, progestins such as progesterone and dydrogesterone can be added for endometrial transformation, and transplantation can be done after 4 days of endometrial transformation. Because the endometrium needs to be evaluated before transplantation, the exact time for transplantation needs to vary from person to person after 28 days of down-regulation, usually 2-3 weeks. If transplantation is needed, it is recommended to follow the instructions of the fertility doctor.