Egg freezing, also called oocyte cryopreservation, is a popular method used by women who want to get pregnant in the future, but medical or other circumstances may prevent natural conception.
The process of freezing eggs is a multistep process that includes three basic steps or processes.
Multiple eggs, up to fifteen per cycle, are removed during retrieval.
Studies show between 25%, and 40% of eggs are lost during thawing.
Studies suggest that each egg a woman freezes has a 4.5 and 12% chance of developing into a healthy fetus carried to term.
With frozen embryos, you have a greater chance (up to 95%) to transfer healthy, fertilized eggs, which improves your chances of pregnancy.
The process of freezing eggs
Freezing eggs is a multistep process that includes three basic steps or processes.
1. Ovarian stimulation
The first step is ovarian stimulation. This is required to trigger the ovaries to release multiple eggs rather than the single egg that is typically released as part of a typical monthly cycle. Your provider will recommend medications that help stimulate the ovaries and prevent premature ovulation. These will help ensure an ideal environment for success during egg retrieval.
During this stage, your provider will closely monitor your health. This may include blood tests to see how you respond to ovary-stimulating medications and tests to check your estrogen levels. Other tests will consist of a vaginal ultrasound to monitor the development of the follicles (the sacs where eggs mature). Once the follicles are ready for egg retrieval, an injection is given to help the eggs mature.
2. Egg retrieval
The second step of the process of freezing eggs is retrieval. This is done at your provider's office under sedation. Multiple eggs, up to fifteen per cycle, are removed during retrieval. Studies suggest that the more eggs retrieved during this step, the better the chances of successful pregnancy and birth.
The final stage, freezing or vitrification, occurs shortly after egg retrieval is complete. Once frozen, the eggs are stored in liquid nitrogen tanks in an embryology lab until you are ready to use them.
Why should you consider freezing eggs?
There are several reasons someone may want to freeze their eggs. Some of the most common include factors in one's life that may prevent them from having a child in the future through natural conception, including medical conditions, gender-affirming surgery, and age.
No sperm required
Egg freezing may be an option for individuals in a same-sex relationship or those who have had (or are considering) gender-affirming surgical procedures that will stop natural egg production. In these cases, eggs can be harvested and frozen before beginning hormonal treatments that will change the function of the reproductive system. In the case of same-sex relationships, frozen eggs can be used to achieve pregnancy without a male partner.
Some women may decide to freeze their eggs to allow for pregnancy at a later date. In today’s corporate world, many women choose careers over children, waiting to have children until they have a successful career. Also, some women may delay or even decide not to "settle down" with a romantic partner. Unfortunately, as a woman ages, the quality and quantity of healthy, viable eggs decrease. Freezing eggs at an earlier age allows for the option of pregnancy when you want it, regardless of your current relationship status.
Easier to reproduce
Egg freezing is the first step in IVF for many people, but the first round of IVF is not always successful. For this reason, women will often complete multiple egg retrieval procedures to ensure they have the most significant opportunities for success.
One key reason someone may choose to freeze their eggs is due to a medical concern or medical treatment that may affect their fertility. For example, certain autoimmune diseases, sickle cell anemia, chemotherapy, radiation, endometriosis, or another surgical procedure that could harm or damage the ovaries.
The drawbacks of freezing eggs
Although there are many potential benefits to freezing eggs, there are also drawbacks and risks associated with the procedure and the health of the frozen eggs. Before choosing egg freezing, you will want to discuss potential disadvantages with your provider so you can understand if egg freezing is the best path for you.
The process of freezing and thawing eggs is not perfect. Not all of the harvested eggs will survive the freezing and thawing process. Eggs are fragile, and it is not uncommon to lose several eggs during thawing. Studies show between 25%, and 40% of eggs are lost during thawing.
Lower chance of pregnancy
It often takes several eggs to result in a successful embryo due to egg loss during freezing, thawing, and transfer. For this reason, the chances of a successful pregnancy from frozen eggs are lower than with other methods. Studies suggest that each egg a woman freeze has a 4.5% and 12% chance of developing into a healthy fetus carried to term.
Freezing embryos – how is it done?
The initial steps of embryo freezing are the same as for egg freezing. The two processes differ because eggs are left unfertilized when frozen, and embryos are fertilized. To create an embryo, a specialist called an embryologist will use one (or more) of the eggs harvested during egg retrieval and fertilize it with sperm from a donor or a partner. Before freezing, the embryo is observed for five to seven days while it grows. After this initial monitoring period, an embryo can be tested for certain genetic conditions and graded to determine which is most likely to produce a viable pregnancy when implanted.
At this point, the highly graded embryos are frozen through a similar process used to freeze eggs. During the vitrification process for an embryo, the water in the cell is replaced with a protectant fluid, and liquid nitrogen is used to flash-freeze the embryo. This prevents ice crystals from forming, which could damage the embryo.
Should you freeze your embryos?
Like egg freezing, embryo freezing has several advantages, some of which make it preferable to egg freezing.
Higher chances of pregnancy
As noted above, when eggs are frozen, several are typically lost during freezing, thawing, or implantation. Because eggs are frozen unfertilized, it is impossible to know in advance if the egg is healthy. With frozen embryos, you have a greater chance (up to 95%) to transfer healthy, fertilized eggs, which improves your chances of pregnancy.
An egg is one single cell compared to an embryo, which is comprised of hundreds of cells. Although the freezing process is essentially the same for the egg and embryo, the structure of the embryo is stronger, which means the embryo is more likely to remain healthy while frozen and during thawing.
More successfully fertilized
Freezing an embryo rather than an egg helps you better understand how many fertilized eggs you have for later use. When you freeze just the eggs, it is impossible to know how many will fertilize successfully. With embryos, you already know how many are fertilized before freezing occurs.
Disadvantages of freezing embryos
When compared to freezing eggs, there are a few drawbacks to freezing embryos that one should consider before deciding which process is best for them.
Creating an embryo requires sperm. This means a woman’s options are a bit more limited when it comes to when and how to use the eggs. It also means a partner or donor must be part of the initial process. This can become a complication if a couple freezes embryos and later separates.
There are also moral dilemmas related to embryo freezing. In some faiths, an embryo is considered life which adds complexity to the decision-making process should you need to or choose to discard extra embryos.
In the end, there is no one “right” answer for which procedure is the better choice. The ideal choice is the one that best fits your current needs and future family planning goals. Both are viable options for starting a family at a later date. It is best to work directly with your reproductive health specialist to learn more about each procedure so you can make the best choice for you.