Objectives: Evaluating pregnancy rates in patients using GnRHa to launch mature ovum antagonist diagnosis at National hospital of obstetrics and gynecology. Materials and methods: A prospective study conducted in 112 women get ovarian stimulation - in vitro fertilization with GnRHa antagonist therapy in National hospital of obstetrics and gynecology from 01/2014 to 01/2015. Results: The result of using Dipherellin group, does not have any cases hyperstimulation syndrome ovarian than 3 cases out of 60 cases with hCG mature ovum. Even to meet normal ovarian stimulation (lower estradiol concentrations 4,000 pg/ml and number of follicles of 14 mm 15 capsules day hCG), mature ovum start with 5,000 IU hCG remains the standard dose risk caused ovary syndrome too heavy to be hospitalized treatment. Conclusion: the use of GnRHa ovarian stimulation cycle - in vitro fertilization by GnRHa antagonist regimens in women with normal ovarian response demonstrated benefits in improving pregnancy rates and limit the risk of ovarian hyperstimulation.