Embryo Cryopreservation and ART Outcome

*Embryology - Theory and Practice*

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cell death.

**Chapter 8**

**Abstract**

ART methods

**1. Introduction**

Cryopreservation

*and Vladislav Dobrinov*

*Iavor K. Vladimirov, Desislava Tacheva* 

The Present and Future of Embryo

Embryo freezing technologies have widely been used in human IVF practice and in animal industry. In this chapter, we will review the development of embryo freezing technology and the application of the method, which will concentrate on discussion of the arguments in favor of and against freezing, as well as the latest results of success rates, comparing them with the other basic assisted reproductive technologies methods. Then, we will present our viewpoint for the future application of embryo freezing methods and their place in reproductive medicine. The analysis of facts and suggestions should enable researchers to rethink the position of cryobiology in reproductive medicine. It should be considered that the method of cryopreservation is not only a technology for storing embryos but also a method of embryo treatment that can potentially improve the success rates in infertile couples. There is also a theory that describes the "treatment" effect of freezing an embryo, which may explain the higher success rates of frozen embryo transfer (FET) compared to fresh embryo transfer (ET). The authors of the "Theory about the Embryo-Cryo treatment" believe that freezing and thawing could activate endog-

enous survival and repair mechanisms in preimplantation embryos.

**Keywords:** embryo, cryobiology, embryo treatment, frozen embryo transfer,

During the last couple of decades, assisted reproductive technologies (ART) have become one of the fastest developing branches of medicine. Since they are the main method of fertility treatment, much research has been done in this area. Enormous amount of work has been done to elucidate the benefits of cryopreservation of stem cells, embryos, gametes, tissues, and organs. The idea of maintaining the viability of living reproductive cells and tissues of various species after long-term storage provides a chance for animal and human reproductive applications [1, 2]. Due to the constantly improving cryopreservation techniques, we are now able to preserve cells and tissues by cooling them to extremely low temperatures, such as −195.79°C (the boiling point of the liquid nitrogen). Cooling down biological objects to such degrees prevents any biological activity, including all the biochemical reactions involved in

Among the biggest scientific achievements, cryopreservation of embryos came into prominence more than 45 years ago [3, 4]. In 1972, Whittingham and associates
