Serum progesterone level above 0.85 ng/mL and progesterone/estradiol ratio may be useful predictors for replacing cleavage-stage with blastocyst-stage embryo transfer in fresh IVF/ICSI cycles without premature progesterone elevation.

Although serum progesterone levels are below the accepted cut-off level of 1.5 ng/mL, there may be reduced pregnancy outcomes in fresh embryo transfer cycles. A threshold level such as 0.85 ng/mL may ensure the decision to replace the cleavage stage with the blastocyst-stage embryo transfer in fresh cycles without premature progesterone elevation.