Elevated E ₂: Oocyte ratio in women undergoing IVF and tubal ET: Correlation with a decrease in the implantation rate

OBJECTIVE: To investigate the influence of various estradiol (E 2 ):oocyte ratios on reproductive outcome in women undergoing in vitro fertilization and tubal embryo transfer (IVF-TET). STUDY DESIGN: Two hundred seven women undergoing 251 IVF-TET cycles were recruited in this retrospective study. All the women received a flare-up gonadotropin releasing hormone agonist (GnRHa) protocol to achieve ovarian hyperstimulation. Oocyte retrieval was performed 34-36 hours after human chorionic gonadotropin (hCG) injection, followed by TET two days later. RESULTS: An E 2 :oocyte ratio ≥ 350 pg/mL had a higher E 2 level (2,213 ± 2,258 vs. 1,553 ± 972 pg/mL, P < .05) and fertilization rate (77 ± 23 vs. 64 ± 23%, P < .001) but a lower oocyte number (4.8 ± 4.7. vs. 7.6 ± 4.8, P < .001) than in those with a ratio < 350 pg/mL. The pregnancy (17.9% vs. 32.8%, P=.03) and implantation (5.3% vs. 12.9%, P =.008) rates were significantly decreased in cycles with an E2:oocyte ratio ≥ 350 pg/mL as compared to those with a ratio < 350 pg/mL. CONCLUSION: IVF-TET cycles with an elevated E 2 :oocyte ratio correlated with lower pregnancy and implantation rates. The poor reproductive outcome possibly was due to the relatively high E 2 concentration, which might have a detrimental effect on endometrial receptivity.