Single Step Protocol and Multi-step Warming Protocol for Blastocyst FET
The Live Birth Rate Between Single and Multi-step Warming Protocol Applied in Blastocyst Vitrification: a Randomized Controlled Trial
Mỹ Đức Hospital
816 participants
Aug 13, 2025
INTERVENTIONAL
Conditions
Summary
The multi-step thawing protocol with a reduction of non-permeable cryoprotectant concentrations to reduce osmotic shock caused by the rapid influx of water. Recent studies have shown that a simplified warming protocol by only a thawing solution gave a comparable survival rate but increased pregnancy rate, reduced patients' waiting time, and decreased the workload of embryologists.
Eligibility
Inclusion Criteria6
- Women aged from 18
- Undergoing no more than 3 previous IVF/ICSI cycles
- Had at least a single good-quality blastocyst frozen.
- Endometrium preparation using artificial cycle
- Agree to single blastocyst transfer
- Not participating in any interventional studies at the same time
Exclusion Criteria3
- Embryos from cycles after in-vitro maturation, pre-implantation genetic testing (PGT)
- Having contraindications for exogenous hormone administration (e.g., breast cancer, thromboembolic disease)
- Having uterine abnormalities (e.g., adenomyosis, intrauterine adhesions, unicornuate/ bicornuate/ arcuate uterus; unremoved hydrosalpinx or endometrial polyp)
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Interventions
Potentially eligible patients' vitrified blastocysts will be thawed by a single-step thawing protocol. For the warming phase, vitrified blastocysts are exposed to the thawing solution of a commercial embryo thawing kit (Irvine Scientific Inc., USA) at 37°C for one minute. Immediately following this, embryos will be rinsed in a 35mm diameter dish of 2ml of pre-equilibrated thawing solution before being placed in culture media in the incubator for at least 2 hours before transfer.
For the MS protocol, thawing kits were equilibrated overnight in a 37°C incubator. Warming procedures utilized the kits (Cryotech RtU, Japan). To remove the cryoprotectants, blastocysts were warmed, and cryoprotectants were diluted in a three-step process. The warming process starts with the exposure of blastocysts to thaw solution (TS) with 1M trehalose for one minute at 37°C. Subsequently, the blastocyst will be transferred to a second well containing a dilution solution (DS) of 0.5M trehalose for a two-minute rinse at room temperature. This is followed by two additional three-minute and 30-second rinses in the wash solution (WS) at room temperature. The timeline for standard warming of blastocysts requires a total of 6.5 min. After thawing, embryo will be placed in the incubator at least 2 hours before transfer.
Locations(1)
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NCT07088640