The meta-analysis comparing the cryopreservation of human embryos by vitrification or slow-freezing suggested that more well design studies as randomized trials are necessary to identify the most successful method for cryopreservation. The efficacy of the vitrification with the GAVI system will be compared with the conventional slow freezing method through a randomized control trial. Couples in IVF attempt will be randomized at the day of embryo cryopreservation by the biologist. Supernumerary frozen embryos will be thawed and transferred in utero in case of failure of the "fresh" embryo transfer. The outcomes of the thawing and frozen/thawed embryo transfer will be assessed. In the two groups, the patients will benefit of the standard IVF procedures applied in the Assisted Reproductive Technologies (ART) center of Toulouse.

The last decade has seen a development of a new cryopreservation technique called vitrification. Despite a lack of randomized control trials comparing slow-freezing and vitrification, vitrification seems to show better recovery rates and pregnancy outcomes. However vitrification is a manual, labour-intensive and highly skilled procedure, results can vary between embryologists and clinics. The GAVI system, an automation instrument with a novel closed system device has been developed. The present study would like to assess the outcomes for embryos automatically vitrification processed with the GAVI system compared with those processed with conventional reference technique of slow freezing.

The meta-analysis comparing the cryopreservation of human embryos by vitrification or slow-freezing suggested that more well design studies as randomized trials are necessary to identify the most successful method for cryopreservation. The efficacy of the vitrification with the GAVI system will be compared with the conventional slow freezing method through a randomized control trial. Couples in IVF attempt will be randomized at the day of embryo cryopreservation by the biologist. Supernumerary frozen embryos will be thawed and transferred in utero in case of failure of the "fresh" embryo transfer. The outcomes of the thawing and frozen/thawed embryo transfer will be assessed. In the two groups, the patients will benefit of the standard IVF procedures applied in the Assisted Reproductive Technologies center of Toulouse.

Inclusion Criteria:

• Couple whose age is > 18 years and who are included in a IVF procedure with the possibility to cryopreserve embryos according to criteria applied at the hospital of Toulouse
• Signed informed consent by both partners in a couple
• Affiliation to a social security scheme for both partners of the couple

Exclusion Criteria:

• Couples who does not meet current requirements described by the bioethics law for accession to the ART procedure
• Positive plasma viral load for HIV, hepatitis C virus or hepatitis B virus during the year before the inclusion in one of the couple.
• One of the two partners (or both) is (are) in safeguarding justice, under guardianship or trusteeship.
• Couple included in another interventional study.