Only extremely high peak serum estradiol adversely affects endometrial receptivity in IVF treatment

Purpose To explore the effect of different concentrations of peak serum estradiol levels on endometrial receptivity quantitatively. Methods In our reproductive medicine center, two best quality of day 3 (D3) embryos were transferred or frozen according to E 2 and progesterone levels on the day of human chorionic gonadotropin (hCG) administration and the number of oocytes retrieved. The remaining embryos were cultured to blastocyst stage and frozen. The patients were then categorized into three groups. The patients with frozen-thawed D3 embryo transfer in artificial cycles without blastocyst frozen served as group 1, those with fresh D3 embryo transfer without blastocyst frozen as group 2, and those with fresh D3 embryo transfer with blastocyst frozen as group 3. Each group was further stratified into 4 sub-groups according to E 2 levels on the day of hCG administration. Clinical pregnancy rate, implantation rate and abortion rate of frozen-thawed and fresh D3 embryo transfer were compared among the three groups in the same stratified E 2 levels. Results For E 2 <7,000 pg/mL, group 1 and group 2 had similar clinical pregnancy rate and implantation rate. But for E 2 ≥7,000 pg/mL, the clinical pregnancy rate in group 1 was significantly higher than in group 2 (p<0.05). For E 2 <7,000 pg/mL, pregnancy rate and implantation rate in group 1 were significantly lower than those in group 3 (P<0.05). But for E 2 ≥7,000 pg/mL, the pregnancy rate in group 1 was significantly higher than in group 3 (P<0.05). There was no significant difference in the abortion rate between group 1 and group 2, or between group 1 and group 3. Conclusions High serum E 2 concentration does not impair implantation and pregnancy rates unless exceeding a certain limit (e.g. 7,000 pg/mL) on the day of hCG administration. Since peak E 2 level was related to OHSS and adverse pregnancy outcomes, further study is needed to set a threshold peak E 2 level for fresh embryo transfer.