The embryo transfer implies transportation from the incubator where they have been at 37 ° C, to the transfer catheter inside a laminar flow hood whose working surface is also maintained at 37 ° C. . From the laboratory to the operating room the embryo is exposed to a temperature drop, and consequently thermal stress occurs, which may compromise its future viability.

The aim of this study is to assess the possible improvement in the clinical results when the embryos are transported in a stable device to avoid the drop in temperature throughout the transfer process.

With the use of this thermosetting device heated to 37 ° C, researchers expect a 15% increase in pregnancy rates.

Inclusion Criteria:

• Cryo-transfer cycles: transfer of embryos vitrified in previous cycles receiving donated eggs inseminated with either conjugal or donated sperm from Instituto Bernabeu bank.

Exclusion Criteria:

• Fresh cycles: transfer of fresh embryos (coming from donated or own eggs), and cryo-transfer cycles from vitrified embryos coming from own oocytes.