Timing of progesterone luteal support in natural frozen-thawed embryo transfer cycles - Back to basics

Abstract

Moderate quality evidence suggests that the administration of progesterone luteal phase support (LPS) is beneficial in natural and modified (hCG-triggered) natural frozen embryo transfer (FET) cycles. There are no comparative studies examining the optimal timing of progesterone LPS administration in natural FET cycles, and the common practice differs greatly between clinics world-wide. In the absence of clinical trials, we aimed to provide a scheme for progesterone supplementation in an attempt to mimic its natural secretion by the corpus luteum. Based on early studies of ovulation physiology, we suggest that progesterone luteal support administration in natural FET cycles should start 36 hours following the onset of the LH surge when measured in a morning serum test, or 36 hours following the administration of hCG for triggering final follicular maturation. Blastocyst transfer should be performed after 5 full days of progesterone supplementation. Randomized clinical trials are urgently required to confirm these recommendations.