Supraphysiological estradiol levels do not affect oocyte and embryo quality in oocyte donation cycles

BACKGROUND: The study aim was to determine whether supraphysiological estradiol (E-2) levels reduce oocyte/embryo quality in oocyte donation cycles. METHODS: A retrospective analysis of 330 consecutive fresh oocyte donation cycles was performed in an assisted reproductive treatment programme between January 1996 and December 2000. Throughout the study period, oocyte donors and recipients followed a standard synchronization regimen that did not vary. A serum E-2 level (peak E-2) was obtained from all oocyte donors on the morning of HCG administration. Peak E-2 values were grouped by 33rd percentile (group I, <1500 pg/ml; group II, 1500-3000 pg/ml; and group III, >3000 pg/ml). All embryo transfers were performed on day 3 after oocyte recovery. RESULTS: Comparisons between groups revealed no significant differences in the quality of oocytes retrieved, and in fertilization rates. Higher peak E-2 levels were directly correlated with a greater number of oocytes retrieved, embryos available for transfer and cryopreservation, and higher average embryo quality scores (P < 0.005). Compared with group I, group III had significantly higher embryo implantation rates (P < 0.05). CONCLUSIONS: Sustained supraphysiological E-2 levels do not adversely affect the quality of developing oocytes and embryos. On the contrary, elevated E-2 levels are associated with a larger number of oocytes and embryos and high-grade embryos for transfer/cryopreservation and, consequently, improved implantation rates.