Impact of Elevated Oestrogen Levels on hCG Trigger Day on Clinical Pregnancy Outcome and OHSS Incidence in Long-Acting GnRHa Down-Regulated IVF/ICSI-ET Cycles.

BACKGROUND

The relevance of oestrogen (E2) levels on human chorionic gonadotropin (hCG) trigger day and clinical pregnancy outcomes was unclear. This study aimed to investigate whether E2 levels on the hCG trigger day affect pregnancy outcome in long-acting gonadotropin releasing hormone agonist (GnRHa) down-regulated in-vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) cycles.

METHODS

This is a retrospective study including 6967 patients undergoing their first long-acting GnRHa down-regulated IVF/ICSI-ET cycles at the Reproductive Medicine Centre of Nanjing Drum Tower Hospital from January 2016 to December 2021. Smooth curve fit analyses were conducted to identify the relationship between serum E2 levels and the clinical pregnancy rate (CPR), along with the live birth rate (LBR). Threshold effect analyses were conducted to figure out potential cut-off values. Further investigation was also carried out for different types of embryos.

RESULTS

Both CPR and LBR declined as the serum E2 levels on the hCG day elevated. CPR reduced significantly when the serum E2 levels exceeded 5000 pg/mL. While considering the influence of different types of transferred embryos, the blastocyst transfer was more vulnerable to the elevation of serum E2 levels than cleavage-stage embryos, and CPR of blastocyst transfer decreased obviously when serum E2 levels were equal to or greater than 5000 pg/mL. Meanwhile, a higher E2 level leads to a higher incidence of moderate or severe ovarian hyperstimulation syndrome (OHSS).

CONCLUSION

The CPR decreased significantly as E2 levels increased with serum E level higher than 5000 pg/mL on the hCG day, which was more obvious in blastocyst transfer than cleavage-stage embryo transfer. In addition, the incidence of moderate-to-severe OHSS also significantly increased. Therefore, the whole embryo freezing might be a better choice in patients undergoing long-acting GnRHa down-regulated IVF/ICSI cycles with higher serum E2 level on the hCG trigger day instead of embryo transfer.