Embryo freezing or cryopreservation

Cryopreservation is the term used to describe the process of freezing and storing sperm, eggs or surplus embryos from an in vitro fertilization cycle.
There are 2 methods currently used for freezing in IVF labs-slow freezing and vitrification (ultra-rapid freezing)
Vitrification is the process of converting something into a solid without any crystal formation. This is done by adding a cryo-protectant. This is important because ice crystal formation can be very damaging to frozen embryos.
Embryos can be frozen at the pronuclear stage (one cell), or at any stage after that up to and including the blastocyst stage (5-7 days after fertilization). Different cryoprotectants and freezing solutions and protocols are used for different stages of embryo development. Many IVF clinics freeze their embryos at the blastocyst stage

Why is this performed?

The very simple answer to this question is the fact that you want to have children later in life or you want to donate.
One knows that fertility decreases with age as the reproductive organ reduces natural preservation of the egg or the sperm. Adding to it, the risk of future problems like diseases, surgeries or radiation which may become a hurdle in the way of becoming a parent. In such situations, this procedure is a boon enabling the joy of being a parent in later years.
Plus, the stored egg or sperm remains of a good quality up to 12 years and are still viable to use.

How is it performed?

The very first thing that you must do before the procedure is to go through a careful screening process of HIV, HVB, HCV etc. to look out for any infection. After this you need a give a written approval of what is to be done with it if you are indecisive or you die, for example- donate it or allow it to be used in research.
The result of the test helps to check the condition of the egg or sperm. It allows the doctor to see the quantity of medication required if any. 
Then, for egg preservation, a woman is given hormones or other medications to stimulate the production of potentially fertile eggs. Then the eggs are removed for embryo formation or for storage.
For egg freezing, the eggs are stored using cryopreservation by ultra-rapid cooling into liquid nitrogen.
For the egg to be converted into an embryo, the retrieved eggs are exposed to a sperm in a mixture made in the laboratory. Fertilization takes around 16-17 hours and the fertilized eggs are called embryos.
After the embryos are formed, an embryologist keeps a check on the embryo over the next 6 days in which the best embryo is selected for either use or preservation.
It is also essential to know that embryos can be frozen in a particular time or up to a particular stage. It can be preserved at a pronuclear stage, when it is the only cell or after that up to the blastocyst stage (5-7 days after fertilization).
Now that the embryo has formed, the process of freezing can begin and the main obstacle is to remove the water. There are two methods for this process, first, slow freezing and second Ultra-rapid freezing or Vitrification.
In slow freezing method, the embryos are protected from damage in sealed tubes and slowly the temperature is lowered. This prevents any damage or aging. However, this method is time-consuming and requires high machinery.
On the other hand, in Vitrification, the embryo is converted into solid without any crystal formation by adding cryo-protectant. It is done because the crystal formation can be very damaging to the frozen embryos making it unusable for the future.
After freezing the embryos, they are stored using cryopreservation.
Sperm freezing is also known as cryopreservation or semen banking is a technique of preserving sperms by freezing and storing in liquid nitrogen at the temperature of -196⁰C that is used on a later date for fertilizing an egg.
Sperm freezing is useful if:
you have a condition or are facing medical treatment for a condition, that may affect your fertility
you are about to have a vasectomy
you have a low sperm count or the quality of your sperm is deteriorating
you have difficulty producing a sample on the day of fertility treatment
you are at risk of injury or death (eg: you’re a member of the Armed Forces who is being deployed to a war zone)


Besides revolutionizing the IVF treatment and fertility preservation, cryopreservation has many associated benefits.
1.The efficiency of assisted reproduction
It allows the practitioner to store the retrieved cells for future uses. Prior to this procedure, the cells could not be stored for further use. Being the process and procedure that are not only tiring but also expensive, one does not have to go with this procedure a number of times.
2.Helps in research
Cryopreservation gives an option to the couples or the individuals to choose to donate their sample to research when required.
3.Reduces health risks
Prior to cryopreservation, it was required to implant all embryos as unused could not be used or stored. This bought along many health risks in the pregnant woman from a miscarriage to weight loss. With this procedure, the sample can be stored reducing any such health risk.
4.Reduces the risk of OHSS
Ovarian hyperstimulation syndrome or OHSS is the major drawback of all assisted pregnancies. It can be reduced by giving a time of rest between egg retrieval and embryo implantation. Cryopreservation allows this time of rest due to its preservation technique which earlier wasn’t possible. 


The success of the procedure, however, does not guarantee that it will have no risks. The cells can be damaged in the freezing state. Most of these damages can be prevented using the cryopreservants, which also protects the cells from further damage.
Some of the most commons risks include damage to the cells as a result of intracellular and extracellular ice formation or dehydration due to movement of water, which can cause direct damage.
 However, it can cause some complication in the person associated with cryopreservation, especially a woman.
1.Conditions related to medications
As already informed, before the process begins the doctor prescribes certain fertility drugs or hormones to the woman, it may result in certain complications including OHSS. The ovaries can become swollen or painful after the retrieval. 
Symptoms like bloating, nausea, vomiting, and diarrhea are the most common.
2.Procedural complications
After the procedure, as a result, there can be certain complications. Bleeding, infection or organ damage can pose a concern.
Q. When should we freeze our eggs?
A. A woman is born with all the eggs that she is going to have which reduces in number over years. Hence, why there is only a 5% chance of getting pregnant at the age of 40’s. So, the best age for egg freezing is between early 20’s to early 30’s.
Q. How long can we preserve our sample?
A. Before the start of the procedure, the doctor checks the condition of the sample and gives you a brief idea of its life. However, an estimate of 10 years is given which can be extended accordingly. Any long-term storage does not hamper the quality of the sample.
Q. Can human organs be cryopreserved?
A. Cryopreservation is used to preserve cells or tissues like cornea. A lot of research can tell if this procedure can work for human organs as well.
Q. What is liquid nitrogen?
A. It is a colorless clear liquid at a low temperature which is used to freeze the sample.
Q. Where are the sample stored?
A. Special cryopreservation tanks are used to store the samples. There are national storage centers wherein they can be stored by long-term.
Q. How can one distinguish between different samples in the storage tank?
A. All the samples are clearly marked with the patient’s information. Further, they are stored according to your future plans. 
Q. Will the baby be healthy or will he have health risks?
A. The babies born with the help of assisted pregnancy will be healthy and will have no special risk factors. They will have similar health risks as a normal baby would.
Q. Are there any negative side effects on the sample if the period of storage is extended?
A. No such damage has been observed. The embryo gains its strength back after being thawed.
Q. How long does it take to recover from the egg retrieval procedure?
A. A day’s rest is expected after the retrieval process. Cramping can last for a few days after the procedure, other than that if you face any other problem, it is better to consult your doctor.
Q. Who is responsible for the freezing and thawing procedure?
A. An experienced, senior embryologist is responsible for the procedure.
Q. How does one know which embryo to freeze?
A. The embryos which reaches a certain level of development are frozen as they have a high chance of surviving the process. Embryos up to the blastocyst day that is 5-7 days after fertilization are generally frozen.
Q. Are the tests necessary before going through the procedure of cryopreservation?
A. The tests are necessary as it allows the doctors to advise if there are any medications required or if there is any disease to be treated. Further, this allows the doctor to suggest the storage time of the sample.
Q. What is done with the sample if the owner dies suddenly without any further information?
A. If there is not proof of the will of the owner regarding the sample, whether it should be donated for research or donated to another couple. Then, in such cases, the sample is to be disposed of.
Q. Is the consent form necessary?
A. One must carry the consent form prior to any procedure in cryopreservation.
Q. What exactly is a cryopreservant?
A. They are a range of solutions in which the tissues or cells are preserved.
Q. Are IVF and cryopreservation same?
A. No, they are not the same. The first step of both the procedures are the same, that is, egg retrieval. However, IVF involves the use of the egg as soon as possible but cryopreservation aims at freezing the sample for future use.

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