You’ve done the heavy lifting, now learn about how your eggs are stored and how to use them in the future
vitrification and cryostorage
Within just a few hours of your retrieval procedure, your eggs are frozen via a laboratory technique known as vitrification (a method of quickly putting eggs into a deep freeze). The vitrification process involves moving your eggs through a series of solutions that gradually eliminate water from them. This causes visible shrinkage in your eggs. These solutions also include a cryoprotectant that permeates the cell membranes of your eggs to replace the removed water and safeguard them (to prevent ice crystal formation).
Next, your eggs are positioned on a specialized vitrification devices (usually 2-3 eggs per device) within a minimal amount of media. As the device holding your eggs is submerged into liquid nitrogen, they are rapidly cooled to -196°C, and the media containing the eggs solidifies into a glass-like bead.
The vitrification devices are individually labeled and placed in a labeled cane that is dedicated to your eggs only. The canes are placed and held in a long-term storage container known as a dewar which has been pre-filled with liquid nitrogen. The dewar is equipped with a 24/7 alarm system to notify embryologists of any temperature fluctuations. Your eggs can be stored there indefinitely until you choose to start a family.
preparing to conceive
timing your pregnancy
Timing of the use of your eggs is completely under your control. The first step we suggest is identifying the month (or even the week) that you would like to undergo the embryo transfer procedure. From there, we will back up 3 months and suggest this to be the time to schedule your first appointment for a preconception and cycle planning consultation. This allows us plenty of time to complete pre-treatment testing (more below).
In parallel to this timeframe you can also be working on optimizing your personal general health. This involves checking in with your primary doctor regarding management or basic screening for any medical conditions and working on personal health outside of the medical office through diet, exercise, sleep hygiene and stress management.
A typical 3 month timeline to using your frozen eggs
testing before pregnancy
expanded carrier screening (ECS)
ECS is a genetic test that checks for a wide range of genetic disorders that a person may carry and could potentially pass on to their children. ECS looks for a broad set of genetic conditions, often numbering in the hundreds. These conditions can include diseases like cystic fibrosis, spinal muscular atrophy, Tay-Sachs disease, and many others.
The test usually involves providing a blood or saliva sample, which is then analyzed to identify any genetic mutations associated with these conditions. The goal is to provide individuals and couples with information about their risk of passing on genetic disorders to their children. Affected individuals could test for the condition via preimplantation genetic testing for monogenic disorders (PGT-M).
Expanded carrier screening (ECS) before creation of embryos informs you of risks for certain inheritable genetic conditions.
Saline infusion sonogram (SIS)
A SIS is a simple office-based ultrasound procedure used to evaluate the inside of the uterus. It involves inserting a small, soft catheter into the uterus through the cervix. Then, a saline (saltwater) solution is injected into the uterus through the catheter, which expands the uterine cavity and allows for better visualization of the endometrial lining (where the embryo will implant).
This procedure can help identify abnormalities such as polyps, fibroids, or uterine adhesions that may not be easily seen with a regular ultrasound.
The inside of the uterus (where the embryo attaches) is evaluated with the use of saline water contrast and ultrasound: saline infusion sonogram (SIS)
turning eggs into embryos
steps in the lab
thaw and fertilization
Just as quickly is eggs go from the retrieval procedure to long term storage, eggs can be taken out of storage and thawed within minutes. The precise day of your egg thaw is based upon your scheduled embryo transfer date which is preplanned and synchronizes your body to the eggs.
Warmed (thawed) eggs are fertilized using a laboratory procedure known as ICSI (intracytoplasmic sperm injection). Here, one by one, each egg is fertilized with one sperm.
Intracytoplasmic sperm injection (ICSI) involves mechanically injecting a single sperm, into a single egg
culture
Within 18 hours of fertilization, eggs that were successful at receiving a sperm will be identified (now as embryos). Embryos are then kept in controlled conditions (media, temperature, humidity, pH) which allows them to naturally develop (cells divide). After a period of 5-7 days and after many cell divisions, some embryos will become blastocysts, the stage at which they are ready for implantation into a uterus.
After 5-7 days of culture, an embryo reaches its most advanced stage called a blasotcyst.
biopsy and embryo chromosome testing
At the blastocyst stage, embryos can undergo optional testing known as PGT-A (preimplantation genetic testing for aneuploidy (PGT-A). Here, a trophectoderm biopsy of the embryo is performed where a few cells (out of 100s) are extracted from the trophectoderm (outer layer of cells which are destined to become the placenta). These cells are then analyzed to determine if the embryo has the correct number of chromosomes (euploid) or if there are any extra or missing chromosomes (aneuploid).
PGT-A is often recommended for individuals or couples undergoing IVF who are at increased risk of having embryos with chromosomal issues, such as advanced maternal age or a history of multiple miscarriages.
Biopsy and testing helps identify embryos with a higher likelihood of implantation success and reduces the risk of miscarriage due to chromosomal abnormalities
embryo transfer
The process of placing the embryo into your uterus (womb) is called an embryo transfer cycle. If you elect to pursue PGT-A (described above) you will undergo a frozen embryo transfer (FET) cycle (meaning embryos are first frozen and then thawed prior to placement in the uterus). Patients foregoing PGT-A can undergo a fresh embryo transfer.
Either way, the uterus needs to be preparred and synchronized with the age of the embryo. This is accomplished through the use of estrogen and progesterone medication which is closely monitored.
Medication preparation for transfer takes about 3 weeks and during this time you will have 2 ultrasound office appointments.
The embryo transfer procedure is a quick and gentle procedure (no anesthesia required). A thin, flexible catheter containing the selected embryo is gently inserted through the cervix into the uterine cavity. Ultrasound guidance is used to ensure accurate placement of the catheter. Once the catheter is in position, the embryo is carefully released into the uterus.
At MFC, a large wall-mounted monitor with a live-feed to the lab bring you face to face with your embryo before the transfer
FAQ
How are eggs physically stored?
Eggs are stored in specially-designed holding tanks called dewars (think of a very large thermos). Individual eggs are organized in groups of 2-3 and each group is placed on a straw-like device (think of a thin, flat and narrow transparent piece of plastic). Freezing devices are then placed and kept submersed in the liquid nitrogen.
How long can eggs be safely kept frozen?
Published case reports suggest that frozen reproductive tissues like eggs can be safely stored for decades.
Can I thaw just a portion of my frozen eggs?
Yes! Your eggs are yours and you can choose to use them in whatever quantities you wish. However we often will recommend thawing an entire cohort of eggs at the same time in order to keep your costs under control (costs are the same regardless of the number of eggs you thaw). You can add multiple cohorts to one embryo creation
Can thawed eggs be combined with addiional fresh eggs in the future?
Yes, some patients who have undergone egg freezing in the past for fertility preservation will then years later undergo IVF for infertility struggles. In this situation it is possible to combine both thawed and fresh eggs together to increase the overall chances of a successful livebirth.
What happens if I don't use my frozen eggs?
If you do not use your frozen eggs, you may choose to donate them to research, another individual or couple,or simply discard them.
I’m ready to get pregnant. Should I try naturally or use my frozen eggs first?
When you’re ready to embark on your family building journey, the top considerations on how to factor your frozen eggs into your plans are 1) how old you were when you froze your eggs? 2) how old you are now? 3) how many children do you want? and 4) how qucikly do you want to become pregnant? Depending upon the answers to these questions we will walk yoiu through arriing at the optimal plan for you as an individual.
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