An interventional study of Standard Vitrification and Ultra-Rapid Vitrification in Infertility, sponsored by Fundacion Dexeus. Recruiting at 2 sites in Spain. Open to female participants aged 18 Years to 50 Years. Per ClinicalTrials.gov, last updated 2026-06-30.
Sponsored by Fundacion Dexeus · Not applicable, Interventional, and Treatment
Blastocyst vitrification is standard in assisted reproduction, but clinical data on ultra-rapid vitrification are limited. This pilot study evaluates the safety, feasibility, and preliminary clinical performance of an ultra-rapid blastocyst vitrification protocol compared with the standard approach.
Blastocyst cryopreservation by vitrification is currently the standard approach in assisted reproductive technology, providing high post-warming survival rates and clinical outcomes comparable to those of fresh embryo transfer. Ongoing refinements of vitrification techniques aim to further improve laboratory efficiency and workflow while maintaining biological safety and clinical effectiveness.
Ultra-rapid vitrification protocols have been developed to shorten equilibration times by modifying exposure kinetics to cryoprotectants, while preserving the fundamental biophysical principles of vitrification. Although ultra-rapid warming protocols are well established, clinical data specifically evaluating ultra-rapid vitrification of blastocysts remain limited.
Moreover, ultra-rapid vitrification requires mechanical collapse of the blastocyst before cooling, introducing an additional embryological manipulation with potential biological implications that warrant careful clinical validation. In this context, the present pilot study aims to evaluate the safety, feasibility, and preliminary clinical performance of ultra-rapid blastocyst vitrification compared with the standard vitrification protocol, prior to broader clinical implementation.
2,085 studies on the registry are indexed under Infertility; 357 are open to participants now.
This study's planned enrollment of 80 is below the median of 135 across 1,412 interventional studies indexed under Infertility.
Browse Infertility studies →Fundacion Dexeus is the lead sponsor of 36 studies on the registry; 6 are open to participants now.
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The standard vitrification protocol corresponds to the routine clinical practice of the laboratory and consists of the following steps: 1. Equilibration step: Blastocysts are equilibrated in Equilibration Solution (ES) for 10-12 minutes at room temperature. 2. Vitrification solution exposure: Blastocysts are then transferred to Vitrification Solution (VS) for a maximum exposure time of 90 seconds. 3. Loading: The blastocyst is loaded onto a Cryotop device (Kitazato). 4. Vitrification: The Cryotop is plunged directly into liquid nitrogen within 1 second of loading to ensure ultra-rapid cooling. 5. Capping: The Cryotop is immediately capped under liquid nitrogen conditions.
Other: Standard Vitrification
The ultra-rapid vitrification protocol is identical to the standard protocol in terms of media, devices, and laboratory conditions, with the following modifications: Preparation step - Blastocyst shrinkage: Prior to equilibration, artificial collapse of the blastocyst is performed using a single laser pulse to induce blastocoel shrinkage. The subsequent steps are: 1\. Equilibration step: Blastocysts are equilibrated in Equilibration Solution (ES) for 2-4 minutes. Vitrification solution exposure: Transfer to Vitrification Solution (VS) for a maximum of 90 seconds. 3\. Loading: Loading of the blastocyst onto a Cryotop device. 4. Vitrification: Immediate plunging of the Cryotop into liquid nitrogen within 1 second. 5\. Capping: Immediate capping under liquid nitrogen.
Other: Ultra-Rapid Vitrification
1. Equilibration step: Blastocysts are equilibrated in Equilibration Solution (ES) for 10-12 minutes at room temperature. 2. Vitrification solution exposure: Blastocysts are then transferred to Vitrification Solution (VS) for a maximum exposure time of 90 seconds. 3. Loading: The blastocyst is loaded onto a Cryotop device (Kitazato). 4. Vitrification: The Cryotop is plunged directly into liquid nitrogen within 1 second of loading to ensure ultra-rapid cooling. 5. Capping: The Cryotop is immediately capped under liquid nitrogen conditions.
The ultra-rapid vitrification protocol is identical to the standard protocol in terms of media, devices, and laboratory conditions, with the following modifications: Preparation step - Blastocyst shrinkage: Prior to equilibration, artificial collapse of the blastocyst is performed using a single laser pulse to induce blastocoel shrinkage. The subsequent steps are: 1. Equilibration step: Blastocysts are equilibrated in Equilibration Solution (ES) for 2-4 minutes. 2. Vitrification solution exposure: Transfer to Vitrification Solution (VS) for a maximum of 90 seconds. 3. Loading: Loading of the blastocyst onto a Cryotop device. 4. Vitrification: Immediate plunging of the Cryotop into liquid nitrogen within 1 second. 5. Capping: Immediate capping under liquid nitrogen.
Post-warming survival rate
the proportion of vitrified blastocysts that remain morphologically viable after warming, expressed as a percentage of all warmed blastocysts.
Time frame: Immediately after warming (within the same laboratory session)
Clinical pregnancy rate per transfer (only first transfer will be considered).
defined as the proportion of embryo transfers resulting in a clinical pregnancy, confirmed by the presence of an intrauterine gestational sac on ultrasound. Only the first embryo transfer per patient is included in the analysis.
Time frame: 6-8 weeks after embryo transfer
Blastocyst re-expansion
defined as the resumption of blastocoel expansion after warming, as assessed by partial or complete reformation of the blastocyst cavity, indicating post-warming viability
Time frame: Within 2 hours after warming
Post-warming blastocyst morphokinetic parameters
Assessment of post-warming embryo developmental dynamics based on time-lapse observation. Morphokinetic parameters will include time to blastocoel re-expansion and time to resumption of blastocyst development, measured in hours from warming to embryo transfer.
Time frame: From embryo warming until embryo transfer (within 2-6 hours post-warming)
Post-warming blastocyst morphological quality
Evaluation of blastocyst morphological quality after warming and prior to embryo transfer. Blastocysts will be graded according to standard morphological criteria based on blastocoel expansion, inner cell mass quality, and trophectoderm appearance. Results will be reported as the proportion of embryos achieving good-quality blastocyst grade per standard scoring system.
Time frame: From embryo warming until embryo transfer (within 2-6 hours post-warming)
Technical or embryological adverse events.
defined as any unexpected or unfavorable technical or laboratory-related events occurring during blastocyst warming, handling, culture, or preparation for transfer, including damage to the embryo, procedural errors, or protocol deviations that may affect embryo viability.
Time frame: From blastocyst warming until embryo transfer, within the same clinical procedure (up to 6 hours post-warming)
Plan to share: Undecided
Started Jun 2026 (actual). Primary completion is estimated for Dec 2027, 18 months after the start.
Of 385 non-industry interventional studies with no phase under Infertility, half reached primary completion within 24 months of starting (the median), counting those still running; a quarter within 10 and three quarters within 46. This study's planned 18 months is below that.
Counting every sponsor, half of 416 studies reached it within 24 months; a quarter within 10 and three quarters within 43.
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