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 :

  • Women who want or need to delay childbearing in order to pursue educational, career or other personal goals.
  • Women diagnosed with cancer, where it should be done prior to chemotherapy, surgery or radiation.
  • Women with a family history of early menopause.
  • 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:

    • 1-2 weeks of birth control pills to temporarily turn off natural hormones (this step can be skipped if there is urgency, such as before cancer therapy).
    • 9-10 days of hormone injections to stimulate the ovaries and ripen multiple eggs.

    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:

    • Usage of cryoprotectants – These cryoprotectants help the egg from forming an intracellular harmful ice crystal when stored in deep freezing.
    • Slow-freezing technique – This technique involves the use of programmable freezers that freeze the eggs very slowly so that the intracellular ice crystals cannot be formed. This technique protects the eggs from exposure to the toxic substances present in the cryoprotectants. In this slow-freezing method, initially, the cryoprotectants are used in a very low concentration. The high concentration of cryoprotectants is only used when there is a gradual decline in the temperature and a decrease in the metabolic rates of the eggs.
    • Vitrification – In this technique, initially, the higher concentration of the cryoprotectants is used with rapid cooling so that there is no time for the intracellular ice crystals to form (currently used & popular technique).

    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.