Infertility
Conditions
Brief summary
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.
Detailed description
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.
Interventions
OTHERStandard 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.
OTHERUltra-Rapid 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. 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.
Sponsors
Fundacion Dexeus
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
FEMALE
Age
18 Years to 50 Years
Healthy volunteers
No
Inclusion criteria
* Recipients of donor oocytes * Blastocysts suitable for cryopreservation
Exclusion criteria
* Cycles involving PGT * Cycles not reaching blastocyst stage.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Post-warming survival rate | Immediately after warming (within the same laboratory session) | the proportion of vitrified blastocysts that remain morphologically viable after warming, expressed as a percentage of all warmed blastocysts. |
| Clinical pregnancy rate per transfer (only first transfer will be considered). | 6-8 weeks after embryo transfer | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Blastocyst re-expansion | Within 2 hours after warming | defined as the resumption of blastocoel expansion after warming, as assessed by partial or complete reformation of the blastocyst cavity, indicating post-warming viability |
| Post-warming blastocyst morphokinetic parameters | From embryo warming until embryo transfer (within 2-6 hours post-warming) | 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. |
| Post-warming blastocyst morphological quality | From embryo warming until embryo transfer (within 2-6 hours post-warming) | 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. |
| Technical or embryological adverse events. | From blastocyst warming until embryo transfer, within the same clinical procedure (up to 6 hours post-warming) | 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. |
Countries
Spain
Contacts
CONTACTMonica Parriego, PhD
CONTACTIgnacio Rodríguez, MSc
Outcome results
None listed