Freeze-all, for whom, when, and how

Abstract

Background: The ‘freeze-all’ practice refers to the cryopreservation of all mature oocytes or viable embryos after ovarian stimulation. The development of the vitrification technique has been crucial to make this approach a reality, since it increases the post-thaw survival rates and permits comparable implantation rates with fresh embryos. Nonetheless, as implantation probabilities are comparable to fresh embryo transfer in normo-responder patients, the freeze- all strategy has demonstrated no benefits overall.

Method: Narrative review in which we give an overview of this approach, discuss recent advances in the field, as well as for whom, when and how it is recommended to emply the freeze-all technique.

Results: However, there is some clinical evidence that shows its feasibility. Thus, it has been demonstrated that elevation of progesterone at the end of ovarian stimulation decreases the implantation rates after the transfer of day 6 blastocysts in fresh and some uterine pathologies; freeze-all is also the preferred option for patients undergoing pre-implantation genetic testing, since there is an improvement of the results and it allows for inclusion of all blastocysts of the cohort. In high responders, the freeze-all strategy optimizes the response whilst also minimizing the risk of ovarian hyperstimulation syndrome.

Conclusion: Due to the different cases that a reproductive expert might encounter, it is essential to highlight benefits and drawbacks of this practice.

Keywords:

• Controlled ovarian stimulation (COS)
• cryopreservation
• embryo implantation
• freeze-all
• fresh embryo transfer
• frozen embryo transfer (FET)
• in vitro fertilization (IVF)
• segmentation

Disclosure statement

The authors declare no competing financial interests.

Additional information

Notes on contributors

Paula Celada

Paula Celada is a gynaecologist specialized in human reproduction and the manager of the international department at IVI Valencia. She joined the team at IVI in 2015.

Ernesto Bosch

Ernesto Bosch is the Director of IVI Valencia, Spain. In January 2000 he joined the team at the Human Reproduction Unit of the Instituto Valenciano de Infertilidad (IVI) in Valencia; and in 2008 he obtained Master’s Degree in Research on Health Sciences, from the Autonomous University of Barcelona.