It is now possible to freeze unfertilized eggs with very good chances for a successful pregnancy several years later after thawing and IVF. This has been accomplished by introduction of the ultrarapid freezing method vitrification. The technique has successfully been used for fertility preservation for cancer patients prior to receiving chemotherapy and radiation therapy but may now also be used for women that want to postpone childbearing due to non-medical reasons. The most important single factor for the fertility potential of any woman is the age and the associated size of the remaining egg-pool, which usually declines faster after the age of 35, Ideally, oocytes should be harvested in the early 30s and we can then store them up until the woman turns 45. We collaborate closely with the IVI clinic in Spain, where they globally have the most experience of oocyte freezing, both in oocyte donation programs and as social egg freezing.
Egg Freezing: Step by step
To help you understand the process of Egg freezing we have written a simple explanation of the main steps in Egg freezing.
To ensure that you are a suitable candidate for oocyte freezing we perform a thorough medical examination to make sure you can potentially benefit from our treatment. The size of the ovarian reserve, containing the resting egg cells is the single most important factor determining if oocyte freezing can be recommended for you. Our aim is to freeze at least 10 egg cells of high quality in each stimulation cycle. At your first visit we will ask relevant questions about your gynaecological history, including questions about previous pregnancies, menstruations and surgery. We will estimate your ovarian reserve by measuring levels of hormones (AMH, FSH) in your blood as well as a detailed ultrasound investigation of your ovaries. By ultrasound we can determine the number of larger, so-called antral follicles of the ovaries, this number is directly related to the ovarian reserve. We will also take samples to rule out that you have any current infection that can possibly impair your treatment. Within a few days we will call you to inform you about the results from the tests and to plan visits for further discussions.
2. Gonadotropin stimulation
By stimulating the ovaries with FSH (follicle stimulating hormone) we encourage several egg cell containing follicles to grow and mature. The hormones that are used are naturally occurring but given as injections and as nasal sprays instead of being secreted by the pituitary gland of the brain. During the gonadotropin stimulation it is important to rest the woman´s own secretion of the gonadotrophic hormones (FSH, LH). This is accomplished by administration of other natural hormones, either a so-called GnRH agonist as a nasal spray for 2-3 weeks or a GnRH antagonist during the time of gonadotropin stimulation. The gonadotropin stimulation lasts 10 to 14 days; throughout this time we follow the development of the follicles by repeated ultrasound examinations and thorough blood work analysis.
3. Oocyte pick up (OPU)
After approximately 12 days of gonadotropin stimulation, several follicles will have reached a size of about 2 cm. This is the time to finalize the maturation process of the egg cell. The final process of maturation is induced by a bolus dose of the gonadotropin LH. Two days later the mature oocytes are harvested using a thin needle on a transvaginal ultrasound probe. This pick up of the eggcells is done under local anesthesia and is not of any discomfort in the majority of cases.
4. Oocyte freezing
Immediately after harvesting the mature oocytes are prepared for freezing and cryopreservation in the laboratory. First, the oocytes are separated from the surrounding so-called granulosa cells by a gentle enzymatic treatment. The oocytes are later submerged into a cryoprotective solution, which will protects them from harmful crystallization during freezing. Later they will be submerged in liquid nitrogen according to the latest protocol for ultra-rapid vitrification techniques. Using this method, the oocyte is frozen to -176 degrees Celsius in less than a second, which minimizes harmful crystal formation. The frozen (cryopreseved) oocyte is later placed inside a sealed small container that bathes safely in liquid nitrogen for several years until its desired time of use.
5. Thawing and IVF
Cryopreserved oocytes keep their quality throughout the entire period of freezing and can later be thawed, fertilized by sperm cells and used in IVF. When we defrost the oocytes they are removed from the liquid nitrogen and heated slowly in a controlled environment. At the same time as the egg cells are thawed they are flushed several times to remove the cryoprotective solution, which is no longer needed. Normally we thaw 2-3 oocytes at a time, this improves the chances of successfully fertilizing an egg cell. A few hours after freezing we fertilize the egg cells using ICSI. A day after fertilization our embryologists study the egg cells under a microscope to determine which ones have developed into high quality embryos suitable for Embryo Transfer (ET). If there are several embryos of high quality they may be cryopreserved for future Frozen embryo transfer.
Last updated: 2016-02-26