Ultra-rapid Blastocyst Vitrification: Pilot Randomized Study

April 22, 2026 updated by: Fundacion Dexeus

Clinical Validation of Ultra-rapid Blastocyst Vitrification: a Randomized Pilot Study in Oocyte Donation Cycles

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.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

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.

Study Type

Interventional

Enrollment (Estimated)

80

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Ignacio Rodríguez, MSc
  • Phone Number: 22029 0034932274700
  • Email: nacrod@dexeus.com

Study Contact Backup

Study Locations

  • Spain
      • Barcelona, Spain, 08028
        • Hospital Universitario Quiron Dexeus
        • Contact:
        • Contact:
        • Principal Investigator:
          • Monica Parriego, PhD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Recipients of donor oocytes
  • Blastocysts suitable for cryopreservation

Exclusion Criteria:

  • Cycles involving PGT
  • Cycles not reaching blastocyst stage.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Standard Vitrification Protocol

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
  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.
Experimental: Ultra-Rapid Vitrification Protocol

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

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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Post-warming survival rate
Time Frame: 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.
Immediately after warming (within the same laboratory session)
Clinical pregnancy rate per transfer (only first transfer will be considered).
Time Frame: 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.
6-8 weeks after embryo transfer

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Blastocyst re-expansion
Time Frame: 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
Within 2 hours after warming
Post-warming blastocyst morphokinetic parameters
Time Frame: 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.
From embryo warming until embryo transfer (within 2-6 hours post-warming)
Post-warming blastocyst morphological quality
Time Frame: 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.
From embryo warming until embryo transfer (within 2-6 hours post-warming)
Technical or embryological adverse events.
Time Frame: 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.
From blastocyst warming until embryo transfer, within the same clinical procedure (up to 6 hours post-warming)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Fundacion Dexeus

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

May 1, 2026

Primary Completion (Estimated)

December 1, 2027

Study Completion (Estimated)

March 1, 2028

Study Registration Dates

First Submitted

April 13, 2026

First Submitted That Met QC Criteria

April 22, 2026

First Posted (Actual)

April 29, 2026

Study Record Updates

Last Update Posted (Actual)

April 29, 2026

Last Update Submitted That Met QC Criteria

April 22, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • FSD-UFV-2026-04

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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