Embryo Freezing

Embryo freezing (embryo cryopreservation) is an infertility treatment available to couples who are not to a certain extent ready to implant their embryos or have excess embryos. Principally, a woman’s eggs and a man’s sperm are retrieved and prepared. The woman is given hormone injections to produce more eggs than during her typical cycle.

The man produces a sample himself or can undergo one of the sperm retrieval methods: Microdissection TESE, Percutaneous Epididymal Sperm Aspiration (PESA) or Testicular Sperm Aspiration (TESA). After the egg retrieval, the follicular fluid is closely examined under a microscope and all of the eggs present are identified. Each egg is washed in a special medium so impurities are removed. These eggs are then transferred to a special incubator where they will remain until fertilization is ready to take place (2-6 hours after egg retrieval). The partner’s sperm are washed and divided into specific amounts per egg. The egg and sperm are then combined in a dish containing a special culture medium (protein, salt, and antibiotics) before being placed back inside the incubator.

Embryo culture is one of the most important stages of IVF. During this process embryos are formed and nurtured until they are ready to be transferred into your uterus. They are formed by combining your eggs and your partner’s sperm in order to produce a fertilized egg or zygote. The culture process lasts 2-5 days and encourages the growth of the zygote into an embryo. An embryologist will monitor your embryos until they are ready. Embryos can be cultured for two, three or five days before transfer/freezing depending on your reproductive history. The survival rate after thawing depends on the quality of the embryos at the time of freezing. Usually, only the best embryos are chosen for freezing so the survival rate is a higher level. Although IVF success rates with frozen embryos are a bit lower than with fresh embryos, they are steadily improving in recent years. Frozen embryo transfer cycle defines the process in which embryos are thawed and then implanted into a woman’s uterus.

The Embryo Freezing Procedure is quite similar to egg freezing and sperm freezing. However, the process can be quite traumatic for an embryo as not all of them survive the freezing or thawing. Each stage of embryo freezing will be explained to you by the specialist when you have a consultation to discuss your options.

The Cost of Embryo Freezing can be quite expensive in countries such as the United States and United Kingdom, especially when combined with other treatments. More and more couples are traveling overseas to take advantage of affordable procedures available in places like North Cyprus and Georgia. Many couples in UK seek embryo freezing in Cyprus to escape their country's expensive IVF treatments and its inflexible laws.

A Good Candidate for Embryo Freezing

Some couples with infertility issues are good candidates for embryo freezing. The cryopreservation of embryos can be very useful in certain situations. During IVF with ICSI (microinjection), only 1-4 embryos are transferred into the uterus. This can channel a surplus of embryos left behind. A couple can choose to freeze embryos for use during a subsequent IVF cycle if the first cycle is not successful. Not all couples have a surplus of embryos, however.

If intended couples do have a excess of embryos, they will need to undergo egg and sperm retrieval, embryo culture and embryo freezing again. A couple may wish to have a second pregnancy using embryos that were formed earlier. Rather than going through the entire embryo freezing procedure again, they can simply go back to the clinic where their embryos are stored. A fresh embryo transfer may not be an option for a variety of reasons.

A good candidate for embryo freezing is a woman who may be at risk of ovarian hyperstimulation that might be complicated by a pregnancy. In this case, all of the embryos would be frozen on day one after fertilization.

Double freezing can be an effective method in such cases. If you are concerned about the potential for multiple births that may result from multiple embryo transfer, embryo freezing is a good way to preserve these embryos for later use.

A good candidate for embryo freezing is a woman in a relationship who desires children but is about to undergo medical treatment that may make her infertile. By freezing her embryos she has the opportunity to become pregnant with a biological child at a later date. Some couples choose to freeze embryos while others choose to donate them to infertile couples or research.

Your infertility specialist will explain the entire process to you so that you understand each stage and are comfortable with this form of infertility treatment and help you decide if it is right for you.

Embryo Freezing Procedure

The embryo freezing procedure is carried out in stages. Embryos can be frozen anytime between one day and 5-6 days after fertilization. Only the most viable ones are chosen for cryopreservation.

The first step of the embryo freezing procedure requires the removal of all the water present inside the cells. Water expands as it turns into ice and this would burst the embryo. So the embryo doesn’t dry up as the water is being removed, a non-expanding antifreeze solution (cryoprotectant) is added as a replacement.

After most of the water has been removed, the embryo is inserted into a vial and then placed in a controlled rate freezer. It is cooled slowly (-0.30C per minute) so the embryologist always has complete control over the embryo freezing procedure. Another advantage of cooling at a slow pace is that it prevents the formation of large ice fragments that could potentially puncture the embryo. The vial is sealed and placed into a labeled metal cane with other frozen embryos before being put into a storage tank.

Embryos are stored at -196°C in liquid nitrogen (a safe and effective coolant). The duration of the embryo freezing procedure takes a few hours. Labeling is very important throughout the entire process. Individual embryos are labeled carefully and identified according to their origin, developmental stage and date frozen to prevent confusion and avoid misidentification.

To ensure your embryo freezing procedure is carried out successfully, steps are taken to minimize technical failure.

· A back-up freezing system is always close by ensuring there are no interruptions to the temperature

· Generators are available in the event of a power outage

· Alarms monitor the liquid nitrogen levels and are designed to prevent premature thawing

When the embryos are ready to be thawed, they are accurately checked and thawed at room temperature. Unlike the embryo freezing which takes a longer period of time, embryo thawing only takes a couple of minutes. Embryo thawing is a very central stage of the frozen embryo transfer cycle. As a general rule, if the embryo survives undamaged (50% or more) then it is worth keeping and proceeding to the next level.

Embryos can actually undergo a significant amount of freeze damage and still lead to a healthy pregnancy. During the embryo freezing procedure, you will begin to take medication enabling your uterine wall lining to prepare for the embryo transfer. The medication prescribed to you will depend on your own unique situation, including factors such as age and regularity of menstrual periods. There are a number of issues related to embryo cryopreservation that you need to be aware of:

· Some or all of your healthy embryos may not survive the freezing/thawing process or they might be damaged too much to continue. Around 20-25% of embryos are lost through the embryo freezing procedure

· The potential risk of birth defects in children born as a result of frozen embryos. Studies do not show any noticeable increase in defects when compared to the rest of the population