Progesterone Concentrations on Blastocyst Transfer Day in Modified Natural Cycle Frozen Embryo Transfer Cycles

(Abstracted from Reprod Biomed Online 2024;49(1):article 103862) With advances in in vitro fertilization (IVF) techniques, it has become safe and efficient to vitrify and warm embryos, and frozen embryo transfer (FET) now has comparable outcomes compared with fresh embryo transfer. A common approach to endometrial preparation for FET is hormone replacement therapy, and because women do not develop a corpus luteum when undergoing hormone replacement therapy–FET, finding an optimal concentration of progesterone is of great clinical interest.