The study was designed to investigate the effect of luteal-phase administration of gonadotrophin releasing hormone agonist(GnRHa) on pregnancy outcomes in in-vitro fertilization-embryo transfer.

Inclusion Criteria:

1. Age < 37 years;
2. One or more high quality embryos have been got in IVF/ICSI treatment;
3. To transfer at lest 2 fresh embryos;
4. Uterine endometrial thickness ≥ 7mm;
5. Patients have signed informed consents.

Exclusion Criteria:

1. ≥3 IVF/ICSI/FET cycles and no pregnancy;
2. Polycystic ovary syndrome(PCOS);
3. uterine malformation;
4. endometriosis
5. patients with a history of recurrent pregnancy loss.