Sydney IVF | Vitrification (freezing eggs and embryos)

Freezing embryos & eggs

An IVF cycle will hopefully produce a number of viable embryos. Those that aren't immediately transferred back to the patient are placed in cryostorage by lowering their temperature to that of liquid nitrogen (-196°C). At this temperature, embryos can be stored until they are needed for later transfer. This process is also used at Sydney IVF on unfertilised eggs.

A tiny droplet of cryopreservant fluid containing an embryo holds to its vitrification hook
A tiny droplet of cryoprotectant fluid containing a precious egg or embryo nestles on the vitrification hook

Shrouded in vapour, the vitrification block sits in its bath of liquid nitrogen

The problem with freezing any cell in the body is that the fluid inside the cells can form ice crystals that expand and damage the cell membranes. Enormous care must be taken to avoid this. In the past this has meant that eggs and embryos were frozen using a slow programmed decrease of temperature using expensive machinery.

What is vitrification?

Vitrification comes from the Latin word vitrum, meaning glass. In the context of freezing embryos, vitrification is the process whereby the solution containing the embryos is cooled so quickly that the structure of the water molecules doesn’t have time to form ice crystals and instantaneously solidifies into a glass-like structure.

Vitrification for the preservation of domestic animal embryos was developed several years ago. Sydney IVF's research department recognised the potential of the technique and spent a number of years developing a suitable protocol for human embryos. Sydney IVF was the first clinic in Australia to introduce embryo vitrification into clinical practice.

Unlike previous slow freeze methods, which took up to two hours to lower the embryo to the correct temperature, vitrification takes just a few minutes. The embryo is suspended in a drop of fluid on a tool with a tiny hook on the end. The droplet is lowered onto a metal block that has been cooled by liquid nitrogen where it hardens into a "glassy" bead.

What does this mean to me?

Rigorous studies at Sydney IVF have shown that a greater percentage of the embryo's cells survive thawing following vitrification than after slow freezing. Live birth rates for 2006 following the transfer of vitrified embryos increased by 50% over those where slow frozen embryos were transferred.