Egg freezing, also known as oocyte cryopreservation, allows women to preserve their own eggs, frozen when they are young and healthy, to help them achieve pregnancy later.
Eggs harvested from the ovaries are frozen unfertilized and stored for later use. A frozen egg can be thawed, combined with sperm in a lab and implanted in the uterus at a later date (in vitro fertilization).
Who should consider egg freezing :
To retrieve eggs for freezing, a patient undergoes mandatory screening in the form of Ovarian reserve testing & infectious disease testing. Post which the procedure is the same as in-vitro fertilization (see IVF Cycle Details). The only difference is that following egg retrieval, they are frozen for some time before they are thawed, fertilized, and transferred to the uterus as embryos.
It takes approximately 3 weeks to complete the egg-freezing cycle and is consistent with the initial stages of the IVF process including:
Once the eggs have adequately matured, they are removed with a needle placed through the vagina under ultrasound guidance. The eggs are then immediately frozen to sub-zero temperature (-196 degrees). This is done to stop all the biological activity in the egg. Various special methods are employed for egg freezing as mentioned below:
Around 75 to 80% of the eggs stay damage-free even after freezing and thawing. When the patient is ready to attempt pregnancy (this can be several years later) the eggs are thawed, injected with a single sperm to achieve fertilization, and transferred to the uterus as embryos.
The procedure of IVF often yields a large number of eggs which may result in a number of viable embryos. Any remaining embryos that are not transferred into the woman’s uterus after a fresh IVF transfer may be frozen or “cryopreserved” in small tubes and kept and stored in the laboratory for future use. Cryopreservation allows the patient to limit the number of embryos transferred “fresh” without discarding the unused embryos that could lead to a future pregnancy. The embryos can be kept in storage for many years.
These frozen embryos can be thawed and transferred into the womb by a simple procedure called FET (frozen embryo transfer). It involves the preparation of the uterine lining without having to undergo the entire procedure of stimulation & egg pickup.
The latest technique of freezing embryos is by vitrification rather than conventional slow freezing which has helped increase the success rates from a mere 25% to almost 55-60%.
Sperm cryopreservation is widely used to store donor & partner spermatozoa before assisted reproductive treatments, for preservation of male fertility before radiotherapy or chemotherapy as eventually these may lead to testicular failure or at times ejaculatory dysfunction. In azoospermic patients who have undergone surgical sperm retrieval techniques, sperm cryopreservation is done to avoid repeated biopsies or aspirations. At our centre, as a routine protocol we freeze a semen sample to avoid any inconvenience due to failed ejaculation on the day of ovum pickup, which may happen in some patients due to stress or any unforeseen commitments that may arise on the day of the pickup.
