Ultra-rapid Blastocyst Vitrification: Pilot Randomized Study

Fundacion Dexeus

Status: Not yet enrolling

Conditions: Infertility

Treatments: Other: Ultra-Rapid Vitrification; Other: Standard Vitrification

Study type: Interventional

Funder types: Other

Identifiers

NCT07556601

FSD-UFV-2026-04

Details and patient eligibility

About

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.

Full 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.

Enrollment: 80 estimated patients

Sex: Female

Ages: 18 to 50 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Recipients of donor oocytes
• Blastocysts suitable for cryopreservation

Exclusion criteria

• Cycles involving PGT
• Cycles not reaching blastocyst stage.

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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80 participants in 2 patient groups

Standard Vitrification Protocol

Active Comparator group

Description:

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.

Treatment:

Other: Standard Vitrification

Ultra-Rapid Vitrification Protocol

Experimental group

Description:

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.

Treatment:

Other: Ultra-Rapid Vitrification