ObjectiveTo investigate whether delaying the start of ovarian stimulation with GnRH antagonist improves ovarian response in poor responders.DesignRetrospective study.SettingAcademic medical center.Patient(s)Thirty patients, who responded poorly and did not get pregnant with conventional estrogen priming antagonist IVF protocol.Intervention(s)Delayed-start antagonist protocol (estrogen priming followed by early follicular-phase GnRH antagonist treatment for 7 days before ovarian stimulation).Main outcome measure(s)Number of dominant follicles and mature oocytes retrieved, mature oocyte yield, and fertilization rate.Result(s)The number of patients who met the criteria to proceed to oocyte retrieval was significantly higher in the delayed-start protocol [21/30 (70%)] compared with the previous conventional estrogen priming antagonist cycle [11/30 (36.7%)]. The number of dominant follicles was significantly higher in the delayed-start (4.2 ± 2.7) compared with conventional (2.4 ± 1.3) protocol. In patients who had oocyte retrieval after both protocols (n = 9), the delayed start resulted in shorter ovarian stimulation (9.4 ± 1.4 days vs. 11.1 ± 2.0 days), higher number of mature oocytes retrieved (4.9 ± 2.0 vs. 2.2 ± 1.1), and a trend toward increased fertilization rates with intracytoplasmic sperm injection (ICSI; 86 ± 17% vs. 69 ± 21%) compared with conventional protocol. After delayed start, the average number of embryos transferred was 2.8 ± 1.4 with implantation rate of 9.8% and clinical pregnancy rate of 23.8%.Conclusion(s)The delayed-start protocol improves ovarian response in poor responders by promoting and synchronizing follicle development without impairing oocyte developmental competence
