In the course of the IVF or ICSI cycle it may happen that a larger number of embryos are obtained than those required to transfer.
In these situations, surplus embryos are cryopreserved and, if possible, transferred later, without the need to resort to new ovarian stimulation.
In certain clinical situations it may be necessary to freeze all embryos and postpone transfer to a later, non-stimulated cycle.
According to the law in force, cryopreserved embryos must be used by the couple in a new transfer, within a maximum of three years. After this period, the embryos can be donated to another couple, used in scientific research or eliminated.
If it is the option of the couple, it is possible to cryopreserve fertilized oocytes before cell division occurs (pre-embryos).