Oocyte and Embryo Freezing: Meet Vitrification

Cryopreservation of oocytes and embryos is a common technique in assisted reproduction centers. At CREA we use vitrification, a technique that freezes the cells extraordinarily quickly, thus avoiding damage to oocytes and/or embryos and, in this way, achieving a higher implantation rate.

What does vitrification of oocytes and/or embryos consist of and when is it performed?

The freezing of oocytes and/or embryos basically consists of freezing embryos and oocytes in liquid nitrogen at a very low temperature (-196ºC) for later use in an in vitro fertilization process.

In both cases, the woman undergoes ovarian stimulation and oocyte aspiration by means of ovarian puncture. Once obtained, the highest quality oocytes are selected for vitrification. In the case of embryo vitrification, the selected oocytes are inseminated with the sperm of the couple or of an anonymous donor and, after that, the resulting embryos are vitrified. On special occasions, for example in the case of oncological patients, it can be performed without prior ovarian stimulation, but ideally it is performed to increase the number of oocytes obtained.

Vitrification of oocytes and embryos is usually performed in these two circumstances:

  • Oocyte freezing to preserve the fertility of women who are going to undergo a treatment that may damage their reproductive capacity (for example, an oncological treatment) or women who wish to delay their maternity for social or work-related reasons.
  • Freezing of viable embryos that are not transferred after an in vitro fertilization process, in order to be used in subsequent cycles.

What is the difference between classic freezing and vitrification?

The classic freezing method consists of cooling from ambient laboratory temperature to minus 200°C and subsequent storage in nitrogen tanks. This process is controlled by a computer that injects nitrogen vapors progressively over several hours at a rate of approximately 0.3°C per minute. However, one of the risks of this procedure is that the surrounding water, and even the water inside the cells, can crystallize, damaging the egg or embryo from the inside. To prevent this from happening, a series of substances known as cryoprotectants are used, but even so, some cells can be damaged and many embryos do not survive the freezing process.

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However, the advantage of vitrification over the classical method lies in the freezing time of the cells. With vitrification, both the eggs and the embryos are cooled to more than 15,000°C per minute, which prevents the formation of ice crystals. In this case, what forms around the embryo is a kind of totally safe gel that facilitates its survival.

Statistically, with the classic embryo freezing method, the implantation rate was approximately one third; embryo vitrification, on the other hand, allows approximately 80% of the embryos to survive the process without problems, which makes it possible for the implantation rate to increase considerably. The data support this: more than half of the women achieve a pregnancy.

CREA, pioneer center in embryo vitrification

Embryo and egg vitrification is a specialized process that requires the latest technology and the most qualified personnel. In addition, the laboratory in which it is carried out must have a system perfectly subject to the highest standards of quality and control so that no errors occur.

At CREA we are pioneers in assisted reproduction and we have a solid professional track record backed by more than 20 years of experience in this field. Among our objectives are to provide the best quality in personalized care, to have greater guarantees of successful pregnancy and to offer patients total security in all our processes.