Euploid programmed frozen embryo transfer cycles are associated with a higher live birth rate when estradiol levels more closely mimic physiology

To determine whether peak estradiol (E2) levels above the usual physiologic range (300-500 pg/mL) will impact programmed frozen embryo transfer (FET) outcomes in an ideal study population of those using good-quality single euploid blastocysts.Retrospective cohort study.University-based clinic.Single euploid-programmed FET done at a single academic institution from January 2016 to December 2019. The population was divided into three groups on the basis of peak serum E2 levels during endometrial preparation: group A (E2 <300 pg/mL), group B (300-500 pg/mL), and group C (>500 pg/mL). Group B was used as the reference range for statistical analysis.Frozen embryo transfer cycles.The primary outcome was the live birth rate (LBR). Secondary outcomes included implantation, biochemical, ectopic, and miscarriage rates.A total of 750 FET cycles were included in this study. Poisson regression analysis showed a negative impact of higher peak E2 on the LBR. A decrease in LBR was noted between group C and referent group B (50.2% vs. 63.4%, risk ratio 0.79 [0.68-0.91]) and group A and referent group B (42.5% vs. 63.4%, risk ratio 0.67 [0.46-0.98]). Secondary outcomes were notable for a lower implantation rate when groups A and C were compared with group B and a higher biochemical rate between group C and group B. There was no notable difference between groups in ectopic or miscarriage rates.Limiting peak serum E2 levels to 300-500 pg/mL during programmed FET cycles is associated with improved LBRs compared with cycles with peak E2 levels of <300 pg/mL or >500 pg/mL in an ideal study population.