Impact of progesterone concentration on human chorionic gonadotropin trigger day on clinical outcomes with one top-quality cleavage-stage embryo or blastocyst transfer in fresh in vitro fertilization cycles.

The progesterone concentration on the hCG trigger day exhibits a curvilinear relationship with pregnancy outcomes in blastocyst transfer cycles, and the optimal threshold of the progesterone concentration is 0.80 ng/mL.