Endometrial receptivity is a limiting step in the success of in-vitro ferti
lization (IVF). To investigate this issue, we selected a specific populatio
n of high responder patients in whom implantation was impaired, even when g
ood quality embryos were transferred, We present a series of studies showin
g that high oestradiol concentrations on the day of human chorionic gonadot
rophin (HCG) administration are detrimental to uterine receptivity, In addi
tion, we suggest clinical strategies to improve endometrial receptivity in
high responder patients using a step-down regimen.