 Women will be randomly divided into two groups; one will be subjected to endometrial preparation by hormone replacement therapy HRT and the other will be subjected to minimal ovarian stimulation MOS. Women in the HRT group will be given estradiol valerate 4 mg daily from day 2 to day 12 of the cycle then the endometrial thickness will be assessed on day 13 by transvaginal sonography TVS. If the endometrium is 8 mm and of moderate echogenicity, luteal phase support using progesterone supplements will be started but if the endometrium is 8 mm, estradiol valerate will be continued until reaching appropriate endometrial thickness and echogenicity then the luteal phase support will be started. Women in the MOS group will be given clomiphene citrate in dose of 100-150 mg daily for 5 days from day 2 to day 6 of the cycle then switched to low dose gonadotropin 75-150 IU daily followed by monitoring of the follicular growth folliculometry ; starting from day 10 of the stimulation cycle and repeated every 2 days. Final oocyte maturation will be induced by administration of human chorionic gonadotropin HCG when there will be at least one leading follicle 18 mm in diameter followed by luteal phase support using progesterone supplements after 48 hours. In both groups, FET will be planned in the appropriate day according to the stage that the embryos have been cryopreserved in it. 