Study of Value of Dexamethasone Used in Ovulation Induction

This study intends to solve the following problems: whether use dexamethasone can obviously decrease transplant cancelling probability in fresh embryo transplant cycle or not, reduce time and frequency going to hospital repeatedly for patients need frozen embryo transplant or not, and reduce the economic burden for patients or not; By comparing pregnancy rate of single transplant, hope to make clear in IVF-ET treatment for patients progesterone increases to a certain level whether it is a good choice to transfer fresh embryo after dexamethasone treatment, or frozen embryo transplant is better.