Egg, Sperm and Embryo Freezing (Cryopreservation)
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Egg, Sperm and Embryo Freezing (Cryopreservation)

Fertility Preservation: Egg, Sperm and Embryo Freezing

Fertility preservation is a process which entails the freezing and storage of sperm, eggs, or embryos for later use for pregnancy. This is an option for individuals who don’t want to have children at this time, who are diagnosed with a condition or advised for a treatment, which may potentially lead to temporary or permanent infertility.

Egg Freezing

Egg freezing, also known as mature oocyte cryopreservation, is a method to harvest eggs from a woman’s ovaries and freeze them to be thawed when she wants to get pregnant later in life. Eggs are frozen because the quality of the eggs decreases with age, which may cause complications during pregnancy or simply prevent it from happening.

Why is Egg Freezing Needed?

There are many factors to apply for egg preservation. These include:

  • Late pregnancy plans: The quality and quantity of eggs decreases rapidly after a maternal age. This may result in infertility or increase the possibility of genetic or chromosomal abnormalities. That’s why egg freezing might be a good option for people who want to consider pregnancy late in life with higher rates of success. 

  • An autoimmune disease: A body suffering from an autoimmune disease, like rheumatoid arthritis, or lupus attacks itself in various places, including ovaries, which may cause fertility-associated conditions, such as endometriosis and premature ovarian insufficiency (POI).

  • A planned gender affirmation surgery: People planning a gender affirmation surgery may freeze their egg to have biological children after their transition.

  • A medical treatment that may affect your fertility: Cancer treatments, like chemotherapy, radiation, or sometimes even hormone therapy may cause temporary or permanentinfertility in women. However, if you are undergoing such treatment, you should consult your doctor about your condition to find out if your treatment is causing infertility. Because being on such treatment does not necessarily harm your ovaries. For example, the NHS states that most radiation therapy treatments don't affect your ability to have children, unless your ovaries are in the treatment area.

  • Being on in-vitro fertilization (IVF) process: IVF is one of many solutions to overcome infertility. It is a multi-step, complex process, which doesn’t necessarily require egg freezing. However, egg freezing might be an option for people who have religious or ethical concerns. Nonetheless, you should consult your doctor if that is a suitable solution for your case.

Egg Freezing Process

  1. Ovarian stimulation

Women ovulate one or two eggs every month. However, one or two eggs is not generally aimed to achieve a successful pregnancy under lab conditions. So, the goal is to retrieve as many eggs as possible. To be able to do so, your ovaries need to be stimulated to ovulate more than 2 eggs. This is achieved by special medications and injections.

It is a safe but unnatural process for a woman, so you will be monitored throughout the process to ensure that desired outcome will be achieved, and your ovaries are not hyperstimulated. For this purpose, regular vaginal ultrasound or blood testing might be asked in your follow-up appointments.

Your follicles will be ready to be retrieved generally after 10 to 14 days.

  1. Egg retrieval

Follicles get ready to be retrieved when they are mature enough. The size they counted as mature is approximately 15-20 mm in diameter. This procedure is performed 2 to 3 days after your last injection with transvaginal ultrasound aspiration method and you will be sedated for the procedure.

During the procedure, an ultrasound probe will be placed into your vagina in order to locate the follicles. Then, a needle will be inserted through your vagina and into a follicle, and an egg will be extracted from the follicle using a suction device connected to the needle. The more eggs retrieved, the higher the chance of pregnancy.

  1. Freezing

After successful retrieval, your eggs are ready to be freezed. However this step requires a special freezing technique called vitrification .It is a rapid cooling process in which special cryoprotectants are used to prevent the formation of ice crystals that damage the eggs during cooling. Then embryos can be frozen and stored immediately in the liquid nitrogen tanks at -321° Fahrenheit (-196.1° Celsius).

What to expect after egg retrieval?

After your eggs are retrieved, your part for the egg freezing process will be finished. You may feel slight discomfort and pain just after the operation. However, you will be able to resume your normal activities within a week.

Since your eggs will be stimulated, you should avoid unprotected sex for a while after your egg retrieval operation

Sperm Freezing

Sperm freezing, also known as sperm banking or semen cryopreservation, is a process where semen is collected via masturbation and freezed to be thawed when one wants to have a child later in life. Semen can be preserved indefinitely.

Why is Sperm Freezing Needed?

You may consider sperm freezing for the following reasons:

  • A medical treatment that may affect your fertility: Cancer treatments, like chemotherapy, radiation, or sometimes even hormone therapy may cause temporary or permanent infertility in men. If you’re about to have such treatments, you may consider freezing your sperm to be able to increase your chance to have a child after your treatment. However, you should consult your doctor because not every cancer treatment necessarily ends up with fertilization-related problems.

  • Vasectomy: Although almost all vasectomies can be reversed, you may still want to consider sperm freezing before your vasectomy operation. You may want to be able to have a child without getting your vasectomy operation reversed or you may just want to keep your options available.

  • Low sperm quality or count: There are several conditions that may lead you to undergo fertilization preservation processes to be able to have a child. One problem would be the low sperm quality and count. You may want to consider freezing your sperm if you’re diagnosed with such a condition, where your sperm count and quality decreases more significantly with age than normal.

  • A planned gender affirmation surgery: People planning a gender affirmation surgery may freeze their sperm to have biological children after their transition.

Sperm Freezing Process

  1. Sample Collection

Sperm can be obtained every single time a man ejaculates. So, masturbation is enough to collect semen sample to be freezed. You will be asked to abstain from ejaculation 2 days prior to your sample collection to ensure the best sperm quality. On the sample collection day, you will deposit your sample to a sterile cup at home or in the clinic as instructed. It is better to do it in the clinic because the faster the freezing step is done, the more live sperm are frozen.

Your sample will be examined to find out sperm quality, quantity, and mobility. Depending on the quality of your sperm, you will be asked to give more samples. Generally, 3 to 6 times of sample collection are required to increase the chances of pregnancy. If you don’t have any healthy sperm in your semen or you’re unable to ejaculate for some reason, your sperm can be surgically retrieved.

Your sample will also be examined prior to freezing to find out if you have any infectious diseases such as HIV, to ensure you are a suitable candidate to be a donor or to prevent contamination of samples from other donors.

  1. Sperm Freezing

Andrologists transfer prepared sperm into small vials containing a specific freezing solution, called cryoprotectant, which will protect and preserve the sperm. The vials are stored in refrigerators containing liquid nitrogen.

Typically, each patient's semen is distributed in different vials and stored in multiple tanks, so the remaining sperm samples will remain safe even if one of the freezers fails or the vials are damaged.

Embryo Freezing

Embryo freezing, also known as cryopreservation, freezes and stores fertilized eggs for future use. An embryo is a fertilized egg, which means it is combined with sperm already. This is another alternative for people who are having infertility problems or are planning a pregnancy for another time.

Why is Embryo Freezing Needed?

You may consider embryo freezing for the following reasons:

  • Pregnancy treatments: There are several treatments offered to people who cannot conceive a child in natural ways. This problem may happen due to several different reasons, therefore, several different techniques are available and offered according to your scenario. In-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are two examples for such fertility treatments. For these types of treatments, embryo freezing could be one of the steps to achieve pregnancy. However, this is not necessarily a must step, especially if you’re not planning the pregnancy at some future time, but right now. You should consult your doctor to find out what kind of journey your treatment will present.

  • Preimplantation genetic testing (PGT): PGT is a series of genetic assays to evaluate abnormalities in embryos that are created during in vitro fertilization (IVF). The purpose is to reduce the risk of pregnancy complications or the possibility of a genetic disease in the embryo prior to pregnancy. It might be recommended by your doctor especially when you have a family history of a genetic condition. This testing process may or may not require embryo freezing depending on the type of biopsy technique for PGT. So, you should consult your doctor if this is the required stage for your scenario. Click to read more on preimplantation genetic testing.

  • Secure the chances for future pregnancy: Some individuals who opt for this operation are undergoing hormone therapy, cancer treatment, gender affirmation surgery, or another medical intervention that affects fertility.

Embryo Freezing Process

Embryo means fertilized egg, so the process of embryo freezing starts the same as egg freezing until egg retrieval step as described above (see the same section in egg freezing). However, there is an additional step before freezing: eggs are fertilized under lab conditions.

Fertilization step can be performed either;

  • Conventional insemination, which is basically overnight incubation of mature eggs with high-quality fresh semen, or

  • Intracytoplasmic sperm injection (ICSI), which is the direct introduction of single healthy sperm to mature eggs.


After the fertilization, the embryo will be ready to be frozen in a few days. Embryos can be sampled for genetic testing at this stage, particularly if the egg or sperm donor is known to be a carrier of specific genetic disorders. The embryos are assessed to identify the healthiest embryos. Those with the highest grades can then be frozen via vitrification method, which is a rapid cooling procedure where a specific freezing solution, called cryoprotectant, is added to prevent ice crystal formation that will damage eggs during cooling. Then embryos can be frozen and stored immediately in the liquid nitrogen tanks at -321° Fahrenheit (-196.1° Celsius).

What are the Risks of Egg Retrieval?

Egg retrieval includes medication and sedation, so you may experience complications associated with these steps. You may also experience infection or insignificant damage where needle and catheter have been introduced. However, all of these cases are very unlikely to occur.

A disease known as ovarian hyperstimulation syndrome (OHSS) can also emerge when ovaries are overstimulated by the drugs. This is why patients are thoroughly watched throughout the procedure. OHSS may cause the ovaries to swell and become painful.

What are the Chances of Success?

The age of the woman when embryos are fertilized has a significant effect on the likelihood of pregnancy following embryo transfer. Eggs collected from women under 35 years old have the highest likelihood of resulting in a pregnancy. Over 95% of embryos that were frozen survive after thawing.

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