Feasibility of a Progesterone-Modified Natural Protocol for Frozen Embryo Transfer: Protocol for a Pilot Cohort Study

Area of Science:

• Reproductive Medicine
• Assisted Reproductive Technologies
• Endocrinology

Background:

• Current frozen embryo transfer (FET) protocols aim to optimize endometrial priming and embryo implantation timing.
• Existing methods like true natural cycle FET (tNFET) and artificial cycle FET have distinct advantages and limitations.
• A novel approach involves initiating luteal phase support before ovulation, bypassing traditional monitoring.

Purpose of the Study:

• To assess the feasibility of a progesterone-modified natural cycle protocol for FET.
• To evaluate the presence of a corpus luteum on the day of embryo transfer as a primary outcome.
• To determine secondary outcomes including clinic visit frequency and pregnancy rates.

Main Methods:

• A prospective cohort study involving 20 women undergoing FET.
• Matching participants to a control group who previously underwent the tNFET protocol.
• Recruitment at The Royal Women's Hospital, Melbourne, Australia.

Main Results:

• Ethics approval obtained July 17, 2024; study commencement September 2024.
• Anticipated study completion and follow-up by September 2025.
• Data collection and analysis will inform future trial design.

Conclusions:

• This preliminary study will guide a future noninferiority randomized controlled trial.
• The trial will compare the progesterone-modified natural cycle FET protocol against the tNFET.
• Further research is needed to establish the superiority of FET protocols.