If you and your partner are struggling to get pregnant, there is hope. Through in vitro fertilization (IVF), many individuals and couples with fertility challenges have gone on to build the family of their dreams. 

During IVF, multiple eggs are harvested from the female and are combined in a lab with the male sperm to create multiple embryos. The more embryos the better chances of success in achieving a pregnancy. These embryos can then be transferred over to the intended mother’s (or surrogate’s) uterus, with the hope that it will develop into a baby. However, your fertility team will only transfer one to two embryos at a time. This means there are usually several embryos leftover from each IVF procedure. These embryos can be preserved for use at another time in the future, for example for another attempt using the frozen embryos during what is known as “FET” (Frozen Embryo Transfer), and this process of preserving surplus embryos for future use is referred to as cryopreservation.

Read more: Egg Donation

But what is cryopreservation? What does this process involve? And is it only reserved for embryos? We answer all of these questions and more below.


Cryopreservation Process

The cryopreservation process is the systematic freezing of eggs, sperm, and embryos for storage and use at a later date. Many individuals and couples choose this process to help achieve pregnancy at a later time. For example, an individual may choose to freeze their eggs before undergoing cancer treatment to preserve fertility. In the following sections, we explore exactly what the cryopreservation process involves.

Read more: Frozen Embryos


Collecting Eggs, Sperm and/or Embryos 

The first step is retrieving the eggs and collecting any sperm that is intended for cryopreservation. In many cases, various embryos are made in the first stages of IVF, which usually means that you have the option to freeze the remaining embryos for use at a later date.

Read more: Fresh Egg Donation

For freezing eggs, the woman will take medications to optimize the number of eggs her ovaries produce. All in all, the same process for egg retrieval in IVF is used for egg retrieval for cryopreservation. For freezing sperm, the male provides the sample through the classic semen collection process, which is then taken through the cryopreservation process. 

For embryo freezing, male sperm and female eggs are collected in similar ways. Yet, the sperm and eggs are combined to create an embryo. Once cell division has reached what is considered exceptional conditions, the embryo then undergoes the cryopreservation process. From there, these embryos are stored at the fertility clinic or a cryopreservation bank until they are requested for use and transferred to the intended mother’s (or surrogate’s) womb.


Cryoprotective Agents

Protecting the egg, sperm, or embryo is critical in the cryopreservation process. This is why cryoprotective agents are used. Generally, cryoprotective agents, CPAs, are fluids that prevent ice crystals from harming the cell wall and destroying the cell or cells when rapid freezing is applied.


Cryopreservation Freezing Methods

There are two different cryopreservation methods used for IVF and other fertility treatments. These are referred to as “slow freeze” cryopreservation and “vitrification” (rapid freeze) cryopreservation.


Slow-Programmable Freezing Cryopreservation

The slow freezing cryopreservation involves the freezing of the eggs, sperm, or embryos across various stages. It starts with the addition of CPAs, followed by a cooling of the cells for two hours. During this time, the machine that cools the cells does so by lowering the temperature by one degree each minute. Once the eggs, sperm, or embryos become frozen, they are then transferred to liquid nitrogen for storage.


Vitrification Cryopreservation

Vitrification cryopreservation is a much faster freezing process. This cryopreservation technique uses higher strength CPAs to avoid damage that can happen due to the rapid freezing of the cells. However, these same CPAs may cause damage which is why the eggs, sperm, or embryos are quickly put in liquid nitrogen, which prevents ice from forming and damaging the cells.


Cryopreservation Storage

Once frozen, the sperm, eggs, or embryos are sealed in liquid nitrogen freezers. Typically, eggs, sperm, and embryos can be kept in this state for many years. However, different countries and states have set limits on how long these cells can be stored.


Thawing in Cryopreservation 

Thawing in cryopreservation is a fairly straightforward process. When the eggs, sperm, or embryos are needed, the thawing process is done slowly in a controlled environment. Through this process, these cells are placed in special fluids that remove any CPAs and that restore the homeostasis, particularly the water balance, of the cell. 


Oocyte Cryopreservation (Egg Freezing) 

For a woman, egg freezing may make sense if you don’t want children now but want the option in the future. Age, illness, and more can impact your fertility. Thus, oocyte cryopreservation can ensure you are able to have the family you’ve always wanted down the road.


How Long Do Frozen Eggs Last? 

In most places, frozen eggs can be stored for 10 years. However, extensions are possible, and this length may vary depending on where you live.  


Sperm Cryopreservation (Sperm Freezing)

The cryopreservation of sperm is used for sperm banks, as well as for males who may want a chance at conceiving with their partner in the future. This can be especially useful if you are about to have certain medical procedures that may impact fertility or the testes.


How Long Does Frozen Sperm Last?

Frozen sperm can typically be stored for up to 50 years. During the thawing process, about 50% of the sperm survive.


Embryo Cryopreservation (Embryo Freezing)

The cryopreservation of embryos is included as part of most IVF programs. By freezing the embryos, you might have another chance at pregnancy or you can plan for the future, especially if you may need to undergo certain medical procedures in the present. 


How Long Do Frozen Embryos Last?

Similar to egg freezing, embryos are often stored frozen for up to 10 years. However, this may vary depending on where you are located. Further, in certain circumstances, embryos may be stored up to 55 years.

The embryo freezing success rates vary depending on what stage the embryo is frozen at. With embryo thawing, research indicates that the average success rate is 69 to 88 percent.


Why is Cryopreservation Done? 

Cryopreservation is an easy way to store donated sperm or eggs, or embryos which can help other couples achieve their baby dreams. It may also be done due to certain medical needs, risk of declining fertility, or simply for a future attempt at pregnancy. Often, the freezing of embryos is used in the IVF process to preserve surplus embryos achieved during treatment, helping many individuals and couples continue to build their families and not have to repeat the IVF process again. 


Advantages of Cryopreservation

Overall, cryopreservation increases the efficiency and effectiveness of fertility treatments by only having to retrieve eggs or sperm once. It can reduce stress on the couple wishing to start or expand their family, as well as provide hope for the future when starting a family might not be possible due to current circumstances. 


At ELITE IVF, our caring and compassionate team is ready to help you grow your family. Our experts have helped countless individuals and couples conceive through fertility treatments and achieve their baby dreams. We have been pioneers in the use of cryopreserved embryos as means of helping intended parents achieve affordable access to fertility solutions using egg donation, transporting cryopreserved donated embryos, eggs and semen around the world safely and efficiently.  Contact us today to learn more.