The transfer of frozen / thawed embryos has been routinely performed in the last 30 years as part of Assisted Reproduction treatment (ART). Currently, more than 50% of couples submitted to ART have surplus embryos eligible for freezing followed by transfer in subsequent cycles. Therefore the selection criteria for the thawed embryos to be transferred must be rigorous in order to maximize pregnancy and of live birth rates. Usually, the evaluation of the embryos before transfer can be performed based on blastomeres survival after a short culture period between thaw and embryos transfer, i.e., 2 to 5 hours, or based on embryo development over a prolonged period of culture (18h to 24h). Post-thaw embryo culture might have an impact on the recovery of mitosis and normal cellular functions. However, until now, there is no consensus in the literature on which post-thaw culture interval has a better impact on pregnancy and live birth rates. Also, blastocysts formation after freezing/thawing of embryos at cleavage stage may bring relevant information about post-thaw culture. Moreover, this strategy can be used as an alternative treatment. Therefore, the authors proposed this prospective randomized, triple-blind study to evaluate the impact of post-thaw embryo culture on the pregnancy and live birth rates.

Inclusion Criteria:

• patients submitted to ART treatment due to infertility that had frozen embryos and need an embryo transfer after endometrial preparation and embryo thawing

Exclusion Criteria:

• patients that does not reach criteria for frozen embryo transfer (thin endometrium, bleeding, inappropriate use of hormones)
• difficult embryo transfer
• embryos that were frozen twice

only women can have an embryo transfer

we don't have permission to share participant data