The goal of this clinical trial is to evaluate whether the direct warming method for frozen embryo transfers (FET) can improve live birth and pregnancy outcomes in women aged 18-45 undergoing IVF treatments. The main questions it aims to answer are:

• Does the direct warming method achieve a similar or higher clinical success rate for FET compared to the conventional multi-step method?
• Is the direct warming method more cost-effective than the conventional method?

Researchers will compare the direct warming method to the conventional multi-step method to see if the former leads to better pregnancy outcomes and reduced procedural time.

Participants will:

• Undergo either the one-step or conventional embryo thawing procedure.
• Complete standard clinical follow-ups for pregnancy, including ultrasound scans and pregnancy tests.

This clinical trial explores a novel direct warming method for frozen embryo transfer (FET), aimed at improving both clinical and operational outcomes in assisted reproductive technologies (ART). The method was designed to simplify and accelerate the embryo thawing process, reducing the time needed for thawing while eliminating the use of cryoprotectants commonly required in conventional thawing methods. This innovation has the potential to offer a more efficient and cost-effective alternative to standard FET procedures.

The primary focus of this trial is to compare the clinical effectiveness of the direct warming method against the conventional multi-step thawing process. In particular, the study seeks to determine whether the new method yields comparable or superior outcomes in terms of clinical pregnancy rate (CPR), ongoing pregnancy rate (OPR), and live birth rate (LBR), while also assessing its overall cost-effectiveness.

Study Design and Technical Details

This study employs a randomized controlled design, with participants being allocated into either the intervention group (direct warming method) or the control group (conventional multi-step thawing). The direct warming method streamlines the thawing process to just 3 minutes, in contrast to the conventional method, which requires multiple stages and takes approximately 20 minutes. By using only an embryo culture medium without cryoprotectants, the direct warming method reduces both complexity and potential risks associated with handling and cryoprotectant toxicity.

Key Objectives

• Primary Objective: To evaluate the clinical efficacy of the direct warming method in achieving comparable or higher success rates for FET as compared to conventional multi-step thawing.
• Secondary Objective: To assess the cost-effectiveness of the direct warming method by comparing the consumable and time costs across different centers.

Expected Impact and Innovation

The direct warming method challenges the traditional multi-step thawing approach, offering a faster and simpler alternative without compromising clinical outcomes. By minimizing the need for cryoprotectants and reducing the complexity of the thawing process, the new method is expected to enhance the overall efficiency of FET procedures while maintaining or improving pregnancy success rates. Additionally, the cost and time savings associated with the direct warming method may make it a viable option for IVF clinics worldwide, driving standardization and consistency across clinical settings.

Inclusion Criteria:

• Plan to undergo single embryo transfer (SET) during the FET cycle.
• Age between 18 and 45 years.
• Patients with at least one high-quality blastocyst available for transfer.
• Patients who have provided informed consent to participate in the study.

Exclusion Criteria:

• Patients with repeated implantation failure (RIF) or recurrent miscarriage (RM).
• Patients with known uterine anomalies or significant uterine pathology (e.g., fibroids, polyps).
• Patients who are unwilling or unable to provide informed consent.

IPD will not be shared due to concerns regarding participant confidentiality and privacy. Additionally, the informed consent process did not include provisions for the sharing of individual-level data with third parties. Furthermore, local regulatory restrictions limit the ability to distribute sensitive health data outside the study team.

In this trial, participants and outcomes assessors will be masked to ensure unbiased results. The embryologists performing the thawing procedures will not be masked, as they are directly involved in applying the assigned thawing method (either the direct warming method or the conventional multi-step method). Additionally, the research staff responsible for enrolling participants will also remain blinded to group assignments to maintain allocation concealment. However, participants who are determined not to be pregnant after embryo transfer may be informed of their group assignment at that time. However, if a pregnancy is confirmed, participants will not be informed of their group assignment until after delivery or in the event of pregnancy loss.