Objective
Edited by: Emre Pabuccu, Ufuk University, TürkiyeReviewed by: Hongzhan Zhang, Shenzhen Zhongshan Urological Hospital, China; Guanhua Qian, Chongqing Medical University, China; Xiushan Feng, Fujian Medical University, China†These authors have contributed equally to this workThe administration of progesterone before transfer in hormone replacement treatment (HRT) is crucial for the clinical outcomes of frozen-thawed embryo transfer (FET), but the optimal duration of progesterone remains controversial. This study aimed to investigate the effect of the duration of progesterone administration on the clinical outcomes of FET cycles.