Efeito do tempo de congelamento após Vitrificação na taxa de implantação e gravidez após transferência embrionária

Abstract

Introduction: Embryo freezing is a routine procedure in Assisted Human Reproduction treatments. The main advantage of embryo cryopreservation is that it minimizes hormonal stimulation and follicular puncture in subsequent cycles. In these cases, it is only necessary to transfer the cryopreserved embryos in a new menstrual cycle. Transfer of thawed embryos allows the use of embryos obtained in a previous treatment cycle and can be performed with embryos at the cleavage or blastocyst stage. Embryo vitrification has proven to be a more effective alternative to slow freezing, not only because it is a simple, lower cost and faster technique, but also because it has higher survival rates and better clinical outcomes. The number of frozen embryos and the time they remain cryopreserved is increasing every day. Although the vitrification technique is promising, it remains controversial whether the time of freezing affects the viability of embryos and the rate of implantation and subsequent pregnancy. Objective:: Evaluate the impact of embryo freezing time after vitrification on implantation rates and clinical pregnancy rates. Methods: A multicenter retrospective study in which medical records of 1568 women undergoing embryo transfer cycles with autologous oocytes during the period from January 2015 to December 2019 were evaluated. Patients were grouped into 4 groups according to freezing time, 0-90 days (840 patients), 91-120 days (308 patients), 121-360 days (172 patients), and above 360 days (248 patients). In each group, subdivisions were made by age group (up to 35 years, 36-40 years, and over 41 years) and stage of freezing and embryo transfer: cleavage stage (D2 or D3) and blastocyst (D5). Results: There was a significant difference between the time the embryos remained frozen and the pregnancy and implantation rates according to patient's age and embryo stage Conclusion: The results suggest that prolonged storage time of embryos negatively affects pregnancy and implantation rates