Fresh embryo transfer versus frozen embryo transfer in in vitro fertilization cycles: a systematic review and meta-analysis.

Introduction Since the first live birth from oocyte cryopreservation three decades ago, oocyte cryopreservation has become an important component of ART. Cryopreservation techniques have evolved, leading to higher success rates and the introduction of oocyte cryopreservation into IVF clinics worldwide. Concurrently, there has been an increase in patient demand, especially for so-called 'social egg freezing' that allows women to preserve their fertility in anticipation of age-related fertility decline. This review addresses a need to evaluate the current status of oocyte cryopreservation. It explores current techniques and success rates, clinical applications, the rise of elective oocyte cryopreservation, and future implications. Methods A search was performed using Web of Science and PubMed databases for publications between January 1980 and December 2015. Keywords used included 'egg freezing', 'oocyte freezing', 'oocyte cryopreservation', 'oocyte vitrification', and 'fertility preservation'. Results The success rate of oocyte cryopreservation has risen, and the increasing use of vitrification offers has improved outcomes, with IVF pregnancy rates now similar to those achieved with fresh oocytes. There are conflicting opinions about the comparative success rates of open and closed vitrification. Patients are accessing and receiving oocyte cryopreservation for a wide range of indications, and there has been a marked increase in patient numbers and oocyte cryopreservation cycles. Oocyte cryopreservation for circumventing age-related infertility is becoming more widely accepted. Conclusion Oocyte cryopreservation is an established component of ART, with vitrification now being the cryopreservation technique of choice. Increasing numbers of women undergo oocyte cryopreservation for both medical and social reasons. It is important to continue auditing outcomes and reporting long-term follow-up of children born from frozen-thawed oocytes.

/pdf/oocyte-cryopreservation-where-are-we-now-3wfoo2f0m2.pdf

Oocyte cryopreservation: where are we now?

https://www.fertstert.org/article/S0015-0282(12)01843-2/pdf

Outcomes of vitrified early cleavage-stage and blastocyst-stage embryos in a cryopreservation program: evaluation of 3,150 warming cycles

http://www.brusselsivf.be/media/docs/publicaties/2014/Stoop%20D%20The%20Lancet%202014.pdf

Fertility preservation for age-related fertility decline

Forty years of embryo transfer in cattle: A review focusing on the journal Theriogenology, the growth of the industry in North America, and personal reminisces

Preservation of female genetics is currently done primarily by means of oocyte and embryo cryopreservation. The field has seen much progress during its four-decade history, progress driven predominantly by research in humans, cows, and mice. Two basic cryopreservation techniques rule the field--controlled-rate freezing, the first to be developed, and vitrification, which, in recent years, has gained a foothold. While much progress has been achieved in human medicine, the cattle industry, and in laboratory animals, this is far from being the case for most other mammals and even less so for other vertebrates. The major strides and obstacles in human and other vertebrate oocyte and embryo cryopreservation will be reviewed here.

/pdf/current-progress-in-oocyte-and-embryo-cryopreservation-by-1vaq52igpf.pdf

Current progress in oocyte and embryo cryopreservation by slow freezing and vitrification

Although 60 years have passed since the first successful freezing of cells, whole organ freezing is in its initial phase. Heat and mass transfer has limited the success of large tissue and organ cryopreservation either by slow freezing or vitrification. In this article we discuss the limiting factors for the successful freezing of whole organs, such as homogeneous cooling rate, supercooling, latent heat, and recrystallization. We show how the use of directional freezing technology provides solutions to these problems. Whole ovary cryopreservation and transplantation has been proposed as a new method for preserving long-term ovarian function as opposed to ovarian cortical slices. Fertility preservation will benefit from the success of whole ovary freezing and transplantation.

Directional freezing: a solution to the methodological challenges to preserve large organs.

Disclosed is a method for changing the temperature of a sample from an initial temperature via an intermediate temperature to a final temperature, one of the initial and final temperatures being above the freezing point of said sample and the other being below the freezing point. The method is for changing the temperature of a sample having minimal dimension in each of two mutually perpendicular cross-sections exceeding 0.5 centimeters, and at least one of the cross-sections having an outer zone and an inner zone.

Methods and device for freezing and thawing biological samples

Cryopreservation of ovarian tissue has been considered experimental for many years, but very recently the American Society of Reproductive Medicine is reviewing the process and perhaps soon will remove the label of "experimental" and recognize it as an established method for preserving female fertility when gonadotoxic treatments cannot be delayed or in patients before puberty or when there is desire to cryopreserve more than just few oocytes. This article discusses in detail the 3 methodologies used for cryopreservation: (a) slow freezing, (b) directional freezing, and (c) vitrification.

https://journals.sagepub.com/doi/pdf/10.1177/1179558119884945

Techniques of Cryopreservation for Ovarian Tissue and Whole Ovary.

A method and a device for improved freezing of biological containing living cells is disclosed. Directional cooling coupled with agitation, preferably rotation, of the vessel containing the biological sample allows for the freezing of large volume samples at much grater rates than before. Whether a sample is large or not, the greater thermal homogeneity during the freezing process as well as the resulting crystal morphology yield a frozen sample which is exceptionally suited for lyophilization.

Amir Arav

Papers

Current progress in oocyte and embryo cryopreservation by slow freezing and vitrification

Directional freezing: a solution to the methodological challenges to preserve large organs.

Methods and device for freezing and thawing biological samples

Techniques of Cryopreservation for Ovarian Tissue and Whole Ovary.

Method for freezing viable cells