This is a pilot study of a novel protocol for preparation of the endometrium for frozen/thawed embryo transfer whereby estrogen is not administered during the proliferative phase and progesterone is administered through vaginal suppositories in accordance with endometrial thickness only, disregarding the day of ovulation. Progesterone supplementation commences once the endometrium is at least 7 mm, a follicle is demonstrated on TVS, and ovulation has not yet taken place. The day of ET is scheduled according to the unit's working days and progesterone suppositories are commenced 48 hours before the scheduled embryo transfer.