Introduction
Embryo freezing, also known as embryo cryopreservation, is the process of preserving an embryo at sub-zero temperatures for storage and later transfer into the uterus. Here we will delve into the basics of embryo freezing, going through the procedures, what to expect, and what you may want to look out for in the process. Whether you’re just beginning to explore fertility options or ready to book an appointment with a fertility specialist, we hope to demystify embryo freezing and help you make informed decisions.
The treatment cycle for embryo freezing can be split up into 4 key stages: 1) stimulate and retrieve, 2) assess and fertilize, 3) screen and freeze, and 4) transfer. We’ll talk about what to look out for at each stage.
Stage 1: Stimulate and Retrieve
Once you’ve selected a doctor or clinic to work with and come up with a treatment plan, you’ll go through a complete health assessment and prepare for treatment. To retrieve eggs for freezing or IVF, the key to success lies in maturing multiple eggs at once. Injections of the natural hormones FSH and/or LH (gonadotropins) are used to stimulate the growth of the ovarian follicles where the eggs reside.
You’ll then learn to inject the medication that stimulates your ovaries to boost egg production and help eggs to mature. The treatment cycle is typically carried out over 2-weeks. In the meantime, you’ll monitor any side effects or discomforts and let your healthcare provider know about them. The clinic will conduct blood tests and trans-vaginal ultrasound to monitor the growth of follicles and ovarian response.
Once the ovaries have grown sufficiently, the eggs are retrieved via an out-patient procedure.
What to look out for
- Single women: In many locations, single women are only allowed to freeze eggs (not embryos). Some even limit the age at which women can legally freeze their eggs or have restrictions to single women fertilizing their eggs.
- Timing and scheduling: Expect follow up visits to the clinic for ultrasound and blood work every 1-3 days during your treatment cycle to monitor progress and determine when your ovaries are mature enough for egg retrieval. This can be very time-consuming and taxing, so you’ll want to plan ahead with work and other commitments.
- Smoking: Smoking could have an adverse impact on the egg retrieval count and quality and the doctor may advise you to refrain from smoking before and during your fertility treatment cycle.
- Ovarian hyperstimulation syndrome: While it’s normal to have skin irritation around the injection site, symptoms like abdominal bloating, nausea, vomiting, diarrhea, and tenderness in the area of your ovaries may mean ovarian hyperstimulation syndrome. [2] Be sure to monitor side effects and reach out to the doctor or clinic if necessary.
- Recovery: The stimulation and retrieval process can be physically taxing, so be sure to take 1-2 days off to rest and recover, and continue to monitor your body for any discomforts. You may also want to consult with your healthcare provider on when you can resume sexual intercourse.
Stage 2: Assess and Fertilize
Sperm is collected on the day of egg retrieval and prepared for fertilization. Your sperm provider or partner should have completed the necessary blood work and urine tests before the collection day. Mature eggs are selected and fertilized with sperm. If the egg is not mature, it will be discarded because it cannot be used for fertilization. The eggs are transferred to the embryology laboratory where they are kept in conditions that support their needs and growth which is very similar to the natural uterine environment.
After fertilization, the embryos develop and divide in culture until they are ready for genetic testing and/or transfer. Embryo development takes about 7 days.
Healthy embryos first reach the blastocyst stage and the embryos are removed from the incubators and their development is assessed. Day 7 is usually the final day of culture when all embryos that have not reached a developmental stage safe for biopsy or freeze will be discarded.
What to look out for
- Immature eggs: Some eggs that were retrieved may not be mature and ready to be fertilized. Those eggs would be discarded. Depending on how many mature eggs are retrieved, you may need to do more than 1 round of retrieval.
Stage 3: Screen and Freeze
Embryos are screened for quality and readiness for freezing and biopsy could be conducted for genetic testing to determine the presence of chromosomal abnormality and genetic disorders. Embryos that are not of sufficient quality by visual assessment will not be frozen and will be discarded.
The embryos are then frozen either by slow-freeze or vitrification (flash freezing) and stored in tanks of liquid nitrogen.
What to look out for
- Embryos may be discarded: To ensure you freeze only the embryos with highest chances of developing healthily, at this stage, embryos may be discarded due to insufficient quality. You may be surprised to find a discrepancy between the number of eggs retrieved from stage 1 and embryos chosen for cryopreservation.
- Method of freezing: The two methods of freezing are slow-freeze and vitrification (flash freezing). Compared to the older slow freezing technique, vitrification reduces the risks of ice crystal formation in the cell and is a more efficient procedure commonly used in the embryology laboratory.
- Cost of storage: Depending on where you store your frozen embryos, price will be different.
Stage 4: Transfer
Once you’re ready to get pregnant, you’ll prepare for the transfer process with your doctor or clinic. Before embryo transfer, the body needs to be prepared for the implantation procedures and may take another six weeks for the transfer to happen. Embryo transfer is a short procedure where embryos are inserted into the uterine cavity via a catheter, similar to a pap smear.
The number of embryos transferred will increase the chances of pregnancy, but will also increase the risk of a multiple pregnancy (e.g., twins, triplets, etc.). Any embryos that are not transferred in the cycle can be frozen for future use
About Sow Fertility: Raising awareness of reproductive health and fertility preservation
Sow Fertility is a femtech startup focusing in the area of reproductive health and fertility issues. We aim to provide comprehensive and reliable information about female fertility, enabling women to make informed decisions on their fertility journey. By working with medical professionals and highlighting fertility research, Sow Fertility aims to offer insights into the latest discussions on the topic. Moreover, we seek to normalize the conversations on fertility preservation and create a supportive community for those who are interested in elective egg freezing.
Citations:
[1] https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/freezing-embryos
