What is embryo freezing?

Embryo freezing/cryopreservation is a reproductive technology used to preserve the embryos resulting from an In Vitro Fertilization (IVF) cycle, which could not be transferred in the cycle they were created for.

The most widely used method for embryo freezing today is vitrification, a type of ultra-rapid freezing method that has many advantages over conventional slow freezing methods.

The high survival rates of embryos post-thaw have allowed IVF cycles to be optimized, which reduces the number of attempts necessary to achieve a successful pregnancy significantly.

Unlike conventional freezing, embryo vitrification can be defined as an ultra-rapid freezing process which has the advantage of avoiding ice crystals inside the embryo thanks to the use of cryoprotectants. The damage these crystals cause in its cellular structures may harm the viability of the embryo.

Nowadays, the vitrification technique is used regularly for both egg and embryo cryopreservation. It has become a basic tool in assisted procreation labs. Thanks to it, embryos can be preserved for later use.

When is it used?

In a cycle of IVF, particularly after ovarian stimulation and egg fertilization, the resulting embryos are cultured for several days.

However, embryos can be cultured for a maximum of 6 days. For this reason, it is necessary to freeze them until we have decided as regards their fate.

Embryo vitrification also provides a solution in case of, for example:

• Transfer cancellation in the same cycle of stimulation. For instance, due to high risk of developing OHSS or due to inadequate endometrial preparation.
• A fresh embryo transfer has been performed, but there are spare embryos that could be transferred in subsequent cycles in case of negative result or because the patient wants to have more children.
• Fertility preservation. Some couples decide to cryopreserve embryos instead of eggs and sperm separately.