Vitrification (Egg Freezing)
The days of the ‘biological clock’ are over. In the past, women were bound by the limitations of time when it came to their reproductive choices. Women who wanted to get pregnant later in life were faced with egg quality issues. Now they have the option of extending their fertility by preserving their eggs at a time when they are much healthier.
Because women’s bodies ovulate the best eggs first, fertility peaks during the mid 20s and begins to decline around the age of 30. By the mid 30s and early 40s, a woman’s chances of getting pregnant using her own eggs dramatically decreases to less than 10%. By the early 40s, nearly half of those eggs contain genetic abnormalities. This way, when a woman freezes her eggs, for example, around the age of 31, she can be assured that the eggs she is storing are the most viable eggs she’ll ever have.
Traditional methods of human egg cryopreservation have met with limited success. An alternative approach to cryopreservation is by vitrification.
Vitrification is a novel technique for freezing human eggs, which is opening the door to long-term human egg storage. Vitrification is the process of cryopreservation using high concentrations of cryoprotectorant with rapid freezing to solidify the cell into a glass-like state without the formation of ice crystals. Ice crystals within an egg can cause damage or cryoinjurie. Furthermore, the rapid freezing bolsters higher egg survival and therefore higher pregnancy rates.
The BioART fertility Centre has expanded its services to include vitrification for patients who may need to preserve their eggs for later use. This would include patients undergoing cancer treatments such as radiation, chemotherapy or surgery that could limit future reproductive potential. Bioart is the first fertility centre in South Africa to have introduced this service .
Benefits of freezing human oocytes:
Formation of donor “oocyte banks” to facilitate and lessen the cost of oocyte donation for women that are unable to produce their own oocytes.
Provision of oocyte cryostorage for women wishing to delay their reproductive choices.
Convenient cryopreservation of ovarian tissue taken from women about to undergo therapy deleterious to such tissue, which may threaten their reproductive health e.g. Radiotherapy/Chemotherapy etc
A covering layer, or ‘shell’ surrounds embryos or blastocysts called the Zona Pellucida (ZP). The zona has an important role in fertilisation as it allows only one sperm to penetrate the zona and enter the egg to achieve fertilisation. It also acts to prevent premature implantation in the Fallopian tube and may help prevent the early embryo from being attacked by cells of the immune system.
The embryos have to “hatch” or break out of the zona in order to embed into the endometrium lining the uterine cavity. This occurs about four to five days after embryo transfer when the embryo is at the blastocyst stage. Naturally this takes place by expanding/contracting of the zona until it distorts, allowing the blastocyst to “hatch”.
If the zona is not functional, this hatching may not occur. It has been reported that up to 75% of normal embryos never hatch through the protective layering of the zona. Laboratory techniques involved in IVF may result in hardening of the zona. In natural fertilsation there are enzymes present within the fluid in the Fallopian tube, which may “soften” the zona. This does not happen in IVF as the tube is bypassed. The zona may also be thicker following IVF, especially in older ladies. Frozen embryos may also have a hardened zona.