Impact of Endometrial Compaction on Clinical Pregnancy Rate in Frozen Embryo Transfers

To find out if the percentage of endometrial compaction is correlated to clinical pregnancy rate in down regulated frozen embryo transfer cycle. Endometrial compaction is the change in endometrial thickness between the end of the estrogen only phase and the day of embryo transfer. In concept, the compaction of the endometrium after progesterone initiation indicates that the endometrium is responsive to progesterone and could therefore be used as a proxy for endometrial receptivity predictability of FET cycle outcome