Hormone Replacement Therapy Versus Minimal Ovarian Stimulation for Endometrial Preparation Prior to Frozen-thawed Embryo Transfer in Non Polycystic Ovarian Syndrome Patients

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.