Progesterone Initiation Timing in HRT-FET Cycles

Standard Protocol for HRT-FET Cycles

• The American Society for Reproductive Medicine recommends continuing Progynova (estradiol valerate) 6mg daily for 12-14 days to achieve adequate endometrial preparation before initiating progesterone 1, 2, 3
• Endometrial thickness should be assessed via ultrasound before progesterone initiation to confirm adequate preparation, with a target thickness of ≥7-8mm and a trilaminar pattern 4, 5

Critical Monitoring Parameters

• The European Society of Human Reproduction and Embryology suggests that embryo transfer timing is critical and should be calculated from the first progesterone dose, with blastocyst transfer occurring 117-120 hours after initiating progesterone 1, 2, 3

Common Pitfalls to Avoid

• Starting progesterone on a fixed cycle day (like day 9) without confirming adequate endometrial preparation risks poor outcomes, as most patients require 12-14 days of estrogen priming before endometrial transformation 1, 2, 3
• Inadequate progesterone duration (<12-14 days in sequential regimens) may not provide adequate endometrial protection 4, 5

Clinical Algorithm for HRT-FET

• The clinical algorithm for HRT-FET involves continuing Progynova 6mg daily for 12-14 days minimum, performing transvaginal ultrasound to assess endometrial thickness and pattern, and initiating progesterone 800mg vaginal daily once adequate endometrial development is confirmed 1, 2, 3, 4, 5