Egg freezing, or oocyte cryopreservation, is a process in which a woman’s eggs (oocytes) are extracted, frozen and stored as a method to preserve reproductive potential in women of reproductive age, who wish to postpone pregnancy to a later date – whether for medical reasons such as cancer treatment or for social reason as employment or studying or even lack of a ready and suitable mate.
Oocyte cryopreservation has advanced greatly over the past few years, with improved overall success of eggs surviving the freezing process. It is also no longer considered an experimental procedure by the American Society for Reproductive Medicine.
The techniques leading to enhanced gamete survival, potential fertilization and live birth rates allow women a much greater degree of autonomy than was possible even in the past few years.
Who Needs Egg Freezing?
You may consider cryopreservation of your eggs for a number of reasons including the following:
- Women with cancer requiring chemotherapy and/or pelvic radiation therapy that may affect fertility.
- Surgery that may cause damage to the ovaries.
- Risk of premature ovarian failure because of chromosomal abnormalities (e.g. Turner syndrome, fragile X syndrome), or family history of early menopause.
- Ovarian disease with risk of damage to the ovaries.
- Genetic mutations requiring removing the ovaries (e.g. BRCA mutation).
- Fertility preservation for social or personal reasons to delay childbearing.
How Is Egg Freezing Done?
The assessment would include blood tests and pelvic ultrasound. This will also help to determine the necessary dose of medications. Ovarian stimulation is carried out in the same manner that is used with in vitro fertilization (IVF), using injectable hormonal medications. Following the stimulation, the oocytes and the surrounding fluid in the ovarian follicles are aspirated vaginally while under sedation.
The maturity of the eggs is assessed under the microscope, and those that are mature are cryopreserved. Currently, vitrification is the method of choice for cryopreserving oocytes, and this is achieved by ultra-rapid cooling into liquid nitrogen where they can be stored.
How Will The Eggs Be Used In The Future?
When the woman is ready to use the frozen eggs to achieve pregnancy, the cryopreserved eggs are placed in warming solution and assessed in a process called thawing.
Those eggs that survived the freezing process are fertilized with intracytoplasmic sperm injection (ICSI), where a single sperm is injected directly into the egg, and the fertilized eggs will grow in culture until the embryo(s) are ready to be transferred into the uterus to achieve pregnancy, typically 3-5 days after fertilization.
What Are The Chances Of A Pregnancy From Frozen-Thawed Oocytes?
Clinical pregnancy rates per oocyte have been estimated between 4-12%. But egg freezing is not a very popular procedure, so more data will be needed to have a better idea on the success rates.
In general, two factors are most important; the age of the woman at the time of freezing the eggs, and the number of available eggs. Remember that older maternal age increases pregnancy associated risks, so the earlier you use your thawed eggs, the better.
Are There Any Fears With Children Conceived Through Cryopreservation?
Available data comparing births resulting from previously frozen oocytes with those from fresh oocytes have not shown an increased risk of congenital anomalies. More long-term data, however, will be needed to further assess these risks.
Risks Associated With The Procedure?
As with IVF, the risk involved is a possible hyperstimulation of the ovaries, which can lead to infection, and bleeding resulting from the egg retrieval procedure.
How Long Can The Eggs Be Stored?
Available data suggests between 4 to 10 years.
How Much Does Egg Freezing Cost?
The cost of cryopreservation will vary from country to country, hospital to hospital and will likely depend on individual needs after initial assessments. In all, expect that it will be a little pricey.