HMG Stimulation Versus HRT for Endometrial Preparation Prior to Blastocyst Transfer in Moderate to Severe IUA Patients

experimental group:Women will be given HMG 37.5-150IU daily followed by monitoring of the follicular growth (folliculometry) when serum Estradiol (E2)\<100pg/ml，progesterone (P)\<1ng/ml. Final oocyte maturation will be induced by administration of human chorionic gonadotropin (HCG) when there will be at least one leading follicle ≥20mm in diameter followed by luteal phase support (using progesterone supplements) after 24 hours.

Women will be given 17 β-estradiol hemihydrate 2 mg and estrogen gel 5 g daily from day 3 of the cycle then the endometrial thickness will be assessed on day 7 by transvaginal sonography (TVS). If the endometrium is ≥ 9 mm, luteal phase support (using progesterone supplements) will be started but if the endometrium is \< 9 mm, estradiol will be continued until reaching appropriate endometrial thickness and then the luteal phase support will be started. The cycle will be cancelled If the estradiol administration \>60 days.