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

Inclusion Criteria: * BMI 18\~23 kg/m2 * Women with moderate to severe IUA as defined by the American Fertility Society classification (1988) * Presence of at least 3 cryopreserved cleavage-stage embryos (including 1 good quality) or blastocysts Exclusion Criteria: * Using embryos from donor oocytes * Preimplantation genetic diagnosis(PGD)/Preimplantation genetic screening(PGS) cycles * Moderate or severe endometriosis * Untreated unilateral or bilateral hydrosalpinx * Uterine adenomyosis, uterine myoma (submucous,intramural myoma \>4 cm),\>1cm septate uterus, double uterus, bicornuate uterus, unicornuate uterus