Role of serum progesterone levels in frozen embryo transfer: an update

Adequate serum progesterone concentrations are critical for optimizing outcomes after FET. Evidence supports a paradigm shift from empirical supplementation to precision medicine approaches based on serum thresholds and patient characteristics. Future research should aim to define universally accepted cutoff values, clarify the role of endometrial versus systemic progesterone, and refine strategies for tailoring luteal phase support in ART.