IVF Spring > Fertility preservation > Embryo Freezing
Embryo Freezing
During a traditional IVF cycle, many more embryos are generated that are required by the prospective parents. These additional embryos can be stored for future use in case the first IVF cycle is not successful. The embryos are tested for quality and the good quality embryos are collected, frozen at temperatures below -196 degrees Celsius and stored away to be available for use at a future time.
What is Embryo Freezing?
During an IVF cycle, a large number of embryos are collected. Of these embryos, only 2 or 3 embryos will be transferred to the woman’s uterus. This is done to maximize the chances of pregnancy and the other is to avoid the risk of multiple births (having 3 or more kids in the same pregnancy).
The embryos that are not used during one stimulated IVF cycle can be cryopreserved and stored over time. This process is known as embryo freezing.
Advantages of Embryo Freezing.
Provide with additional cycle opprtunities
In case fresh embryo implantation is unsuccessful, frozen embryos may provide the opportunity of trying embryo transfer again without going through ovarian stimulation medication.
Inexpensive than fresh cycles
The overall cost of the IVF treatment is reduced as there are fewer monitoring visits and no need for egg collection, insemination or embryo culture.
Allow gentic testing
If you have a risk of transferring certain genetic conditions to your baby, frozen embryo allows genetic testing for any defects.
Who is Embryo Freezing Suitable for?
Embryo Freezing is suitable for patients who:
- Already are undergoing IVF or ICSI treatments and would like an option to use the excess embryo if the first IVF cycle was not successful
- If you are having treatment for a disease that could affect your fertility (cancer treatment, hormone treatment)
- If you work in hazardous environments that could affect your future ability to have children
- Suffer from Ovarian Hyper Stimulation Syndrome (OHSS)
Embryo Freezing Process
Embryos can be frozen at any stage from Day 1 to Day 6 after egg retrieval. Embryos are tested for quality before they can be frozen. Better quality embryos have a better chance of surviving the freezing and thawing process so that they can be used for future pregnancies. The Embryo freezing process is as follows:
- Gametes of both parents are combined at an early stage, the embryo is frozen to temperatures of – 196 degrees Celsius in liquid nitrogen. Since the lower temperatures do not allow for biological activity the embryos can be stored at this stage for a long time.
- Embryos are transferred to a dish where they are placed in a cryoprotectant that allows them to survive the freezing (vitrification) process.
- Once frozen the embryos can be stored for a period of more than 10 years (although it is recommended to not use embryos which have been frozen for more than 5 years)
- When the embryos are required to be used they you have to begin the thawing process. The embryo thawing process is the reverse of the freezing process where the embryos to be used are removed from their storage and warmed to be used.
- During the thawing process, the cryoprotectant has to be removed so the embryos are carefully passed through solutions that help in this process.
- The thawed embryos are kept in the incubator until the embryo transfer, during which time they resume development and may undergo more cell division.
- Thawed embryos are then transferred to the host for the conception process to begin.
- The timing of the embryo transfer depends on a number of factors including the cell stage of the embryo when frozen and uterine receptivity.
- For women with irregular cycles or with ovulation dysfunction, Frozen-Thawed Embryo Replacement is carried out after medicated endometrial preparation or after a cycle of ovulation induction.
Success of Embryo Cryopreservation and Thawing
Success rates of using frozen embryos for pregnancies are increasing on a regular basis. Success rates of frozen embryos can be said to be comparable to using fresh embryos under most circumstances. For women above the age of 38, the success rate of using embryo cryopreservation and thawing for pregnancies are much higher as the embryos used will have been frozen when they were much younger.