The association of peak serum estradiol levels with pregnancy rate in programmed euploid embryo transfers

Over the last decade, there has been a rise in the application of vitrification and preimplantation genetic testing, leading to increased rates of frozen embryo transfer (FET) cycles and therefore programmed FET cycles.1,2 Exogenous estrogen replacement in programmed FET cycles is done orally, vaginally, and/or parentally (transdermal route). Prior meta-analysis has shown no difference between various supplementation and success rates.3 However, serum estradiol (E2) levels are highly variable among patients using exogenous estrogen supplementation and it is unknown whether varying serum levels will alter the endometrial milieu and therefore impact pregnancy outcomes in programmed FET cycles.