GnRH antagonists followed by a decline in serum estradiol results in adverse outcomes in donor oocyte cycles

BACKGROUND: The aim of this retrospective study was to assess clinical outcomes using GnRH antagonists in oocyte donation cycles. METHODS: Between July 2000 and June 2001, 40 recipient cycles generated from donor oocytes were evaluated. Controlled ovarian hyperstimulation (COH) was started on cycle day 2 using recombinant gonadotrophins (225 IU daily). GnRH antagonist was started on cycle day 6 of COH. All recipients were synchronized to donors using GnRH agonist followed by estrogen and progesterone supplementation. Main outcome measures were days of stimulation (DOS), number of ampoules used, peak serum estradiol, number of oocytes, fertilization rate, embryo score, clinical on-going pregnancy rate and implantation rate. RESULTS: Thirty-seven donor cycles (93%) underwent oocyte retrieval, resulting in 36 embryo transfers. Fourteen cycles (35%) had decreased serum estradiol after initiation of GnRH antagonist. No differences were seen in numbers of FSH ampoules, DOS, peak serum estradiol, number of retrieved oocytes, fertilization rate and embryo quality. However, clinical pregnancy rate per initiated cycle [14% (2/14) versus 54% (14/26)], ongoing pregnancy rate per initiated cycle [7% (1/14) versus 46% (12/26)] and implantation rate (4 versus 24%) were all significantly less (P <0.05) following a decrease in serum estradiol after initiation of GnRH antagonist. No clinical predictor, including donor age, basal day 2 FSH or estradiol, ovarian morphology or serum estradiol prior to GnRH antagonist, was predictive of a decline in serum estradiol following GnRH antagonist. CONCLUSION: These data demonstrate an adverse effect on clinical outcome in cycles, resulting in a decline in serum estradiol after GnRH antagonist administration. This effect was unpredictable and provided a simplified protocol for oocyte donation cycles; nonetheless, further study is needed to clarify the adverse effects of GnRH antagonists in oocyte donation cycles.