- What is Vitrification?
- The Vitrification Process
- Vitrification of Oocytes
- Vitrification of Embryos
- Advantages of Vitrification
- Difference between Vitrification & Cryopreservation
- Vitrification at Medicover Fertility
What is Vitrification?
Vitrification is an amazing breakthrough for preserving oocytes (egg) and embryos, and this process has transformed today’s ART industry. It is an advanced technique that leads to a glass-like formation. The word "Vitrification" comes from the Latin word ‘Vitrum’ meaning glass. In this case, the process of freezing happens so rapidly that the water molecules don’t get the time to form ice crystals, but instead immediately solidify into a glass-like structure thus avoiding freezing injuries to the eggs or embryos.
The vitrification process
Vitrification has now become a potential alternative to slow freezing, and the process is explained in the following steps:
- The eggs or embryos are exposed to a high concentration of cryoprotectants, which allows rapid dehydration of the reproductive cells.
- The eggs or embryos are then loaded into tiny storage devices that will facilitate ultra-rapid cooling.
- The storage devices containing the eggs/embryos are cooled as fast as possible at around 1000 degrees per minute.
- The high cooling rate combined with the use of high concentrations of cryoprotectants allow the contents of the storage device that is oocyte/embryo and the fluid to turn into a glass-like substance instead of ice.
- Then they are stored in sealed casting that is kept in liquid nitrogen.
- When needed, the oocyte or the embryos are quickly warmed up to body temperature, and the preservative is washed away.
- After 3-4 hours, the eggs can be injected with a single sperm, and the embryos can be transferred to the uterus immediately.
Vitrification of oocytes
Vitrification is a complicated procedure than slow freezing, but this technique preserves and keeps the eggs completely fresh even after a few years. It has also been seen that pregnancy success rates from vitrification can be compared to fresh IVF cycles.
The underlying problem with freezing eggs, versus sperm or embryos, is that eggs are mostly made of water. Because of this, ice crystals would form when freezing was attempted, and these crystals would damage the cell’s structure, making them unusable. Even though doctors try to remove the crystals as they thaw the egg, but the pregnancy outcomes of these eggs were found to be very poor.
The key to the whole process is a smooth transfer of the natural fluid out of the egg, while it is made sure that the anti-freeze is slowly flowing in at the same time. Once this step is carefully done, the eggs quickly freeze or vitrify. This quick cooling keeps the ice crystals from forming that could have damaged the delicate cellular parts of the eggs. Nowadays vitrification of oocytes has become a standard part of infertility treatment.
Vitrification of embryos
Vitrification of embryos is done to preserve the excess embryos. In IVF, the practice is to transfer a smaller number of fresh embryos in the uterus to minimise the risk of multiple pregnancies. If the first cycle fails then without undergoing the hassles of ovarian stimulation again followed by egg retrieval, a frozen embryo transfer can be done.
Vitrification plays a significant role in the medium to severe cases of ovarian hyperstimulation syndrome (OHSS). In approximately 5-10% of cases ovarian hyperstimulation, i.e. excessive reaction of the ovaries to hormonal stimulation, occurs in women undergoing extracorporeal (occurring outside the body) fertilisation. In such situations, it is not advisable to transfer fresh embryos due to medical reasons. Therefore, all embryos are frozen and transferred after hyperstimulation has entirely subsided. In cases of polyps and hydrosalpinx, a doctor recommends frozen embryo transfer (FET).
Advantages of vitrification over slow freezing
The main advantages of vitrification over slow freezing are:
- No ice crystals are formed which can damage the eggs or embryos.
- It also eliminates the use of the expensive freezing unit that is required in the process of slow freezing.
- Post-thawing, the survival rate of the oocytes and the embryos, are found to be higher.
- It has also been found that the pregnancy outcome of vitrified embryos is higher than slow freezing. Because in slow freezing, approximately 20-30% of embryos do not survive after the thawing process.
The difference between vitrification & cryopreservation
|1) Vitrification is a modern technique of cryopreservation that involves sudden cooling of reproductive cells to -196℃ within seconds.||1) It is a technique of slow freezing of reproductive cells in a special medium and then storing them in liquid Nitrogen at -196℃|
|2) In vitrification a medium containing a high dose of cryoprotectants is used, which protects the cells from damage.||2) In slow freezing ice crystals are formed which can adversely affect the quality of frozen oocytes and embryo and hence reduces the chance of pregnancy.|
Vitrification at medicover fertility
At Medicover Fertility we have a highly equipped lab with state-of-the-art equipment which consists of high-end incubators for culturing of oocytes and embryos and vitrifies for cryopreservation.
Vitrification is a very intricate procedure; hence is a delicate art to master. Our Embryologists are internationally trained and follow the best global practices with the latest technology. At Medicover we have been using vitrification in freezing both the oocyte and embryos. Moreover, the embryologists are available 24x7 to monitor the embryos/oocytes. Medicover Fertility has successfully conducted numerous vitrified embryo transfers with a high pregnancy outcome.