Oocyte Cryopreservation : Preserving Reproductive Potential
Not ready to have a baby right now because you are focused on your career or haven’t found the perfect match? Cryopreservation may be the right choice for you. The concept of “fertility preservation” offers hope to women who previously had limited or no options for the future creation of a family. Women can potentially pursue their reproductive lives at their own pace, rather than according to the obligations of biology.
Women and men who require chemotherapeutic treatment or radiation that may permanently destroy future fertility as well as women who wish are single or wish to postpone childbearing for personal choices, may preserve their fertility through egg or sperm freezing.
Specific medical indications for fertility preservations are as follows:
- As the number of cancer survivors rises with improved treatments, the greater the number of women and men there are who suffer from premature ovarian failure or testicular failure secondary to gonadotoxic treatment
- Non-malignant conditions
- A number of autoimmune conditions and blood diseases may require systemic chemotherapy which are gonadotoxic (can compromise future fertility)
- Fertility decline with advancing age
- Advancing age confers the worst prognosis for fertility due to an increasing number of aneuploid (genetically abnormal) eggs. This is commonly seen as many women postpone childbearing to obtain an advanced education, prioritize their careers or due to lack of partner
Cryopreservation of Oocytes
Harvesting and freezing mature oocytes (or embryos) is the most effective fertility preservation approach women have currently available. Similar to IVF, injectable medications are administered to stimulate the ovaries followed by the egg retrieval under ultrasound guidance. The embryologist prepares the eggs for freezing by removing the cells surrounding the eggs to better evaluate the stage of maturity. Immature eggs can be cultured to mature in vitro. Only mature eggs are frozen, since only mature eggs can be fertilized.
The eggs are treated with cryoprotectants, which are substances that will dehydrate the eggs in order to prevent formation of ice crystals that can later damage the egg. The eggs will then undergo vitrification, or flash freezing, and stored in a nitrogen tank until ready for use.
Cryopreservation of Sperm
Unlike women, men do not need to undergo hormonal stimulation to retrieve sperm. For men, the process is much simpler and involves 3-5 days of abstinence followed by collection of the ejaculate after masturbation. We usually recommend collecting more than one sample for future use. Similar to eggs, cryoprotectant is added to reduce the formation of ice crystals which can damage sperm. Rapid freezing (vitrification) is performed followed by storage in a nitrogen tank.
There is no limit to how long egg and sperm can be frozen. Once you are ready to conceive, your eggs or sperm are thawed in preparation for fertilization. Not all gametes will survive the thaw process and there is a natural attrition to the IVF process. Egg and sperm freezing cannot guarantee you will have a child. During your consultation, we will discuss specific success rates based on your age, fertility evaluation and goals to help tailor specific recommendations to maximize your treatment outcomes.