Procedure of embryo thawing. The embryologist locates and retrieves the straw containing the frozen embryos from the liquid nitrogen bank (Eugonia archive).

During an IVF cycle it is very common to have surplus embryos of good quality after the performance of the embryo transfer. These embryos can be frozen and stored in an IVF laboratory, either using a programmable freezer or using a rapid freezing method called vitrification. The embryos are stored in large dewars with liquid nitrogen (-196oC).

Cryopreservation of embryos offers us several possibilities:

• The storage of surplus embryos of good quality
• Postponing embryo transfer is special cases like poor endometrium, or severe OHSS.
• The preservation of reproductive potential of a woman prior to chemotherapy, radiotherapy or ovariectomy.

Cryopreservation complements other ART methods and allows the increase of cumulative pregnancy rates, reducing hormone administration and the total cost.