Received April 16, 2025
Accepted November 21, 2025

Introduction: Embryo vitrification is an established procedure which enhances, pregnancy and birth rates. Freeze and thaw cycles have increased tremendously over the years. However, the relationship between embryo viability, implantation rates, and cryopreservation duration remains unclear. Objective: To assess whether the storage time by vitrification affects pregnancy and implantation rates. Methods: This multicentric retrospective study involved 1568 cycles of autologous frozen embryo transfer between 2015 and 2019. Patients were divided into groups based on storage time to assess its impact on pregnancy and implantation rates. Outcomes were maternal age, cryopreservation stage, and embryo transfer stage. Logistic regression was used to investigate associations between storage duration, patient age, and transfer outcomes. The study was approved by the Research Ethics Committee of UFMG and informed consent was waivered. Results: The storage duration of embryos showed an inverse association with pregnancy and implantation rates, correlating with patient age and embryo stage at the time of transfer. Patients aged 36 to 40 and those over 41 years old had lower rates of clinical pregnancy compared to those under 35 years of age Additionally, vitrified embryos transferred at the cleavage stage demonstrated lower rates of clinical pregnancy and implantation compared to those at the blastocyst stage. These results suggest that storage duration, patient age, and embryo stage significantly influence frozen embryo transfer (FET) outcomes. Conclusion: Storage duration, patient age, and embryo stage can affect FET outcomes, with older women and embryos at the cleavage stage possibly experiencing lower pregnancy and implantation rates after extended storage.