The proposal of this study approved by our institutional review boards and institution's ethical committee, and all participants will sign a written consent before enter to study. All patients will be randomly divided into two groups of thawed cleavage embryo transfers and transfers of blastocysts from thawed cleavage embryos. Embryos will be transferred in hormone replacement cycles. Preparation of the endometrium will be started in the second day of menstruation and will be continued according to their transfer type (blastocyst or cleavage). βhCG will be assessed 14 days after embryo transfer. Treatment cycle outcomes will be compared between 2 groups.