JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):241
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263840

P-229. The influence of Atosiban Acetate on implantation rates in frozen-thawed embryo transfer

Angelo Enrico Steckelberg Pimenta Macedo¹, Ana Elisa Vasconcelos Gavião¹, Giulia Savassi Salce¹, Camila Dutra Francisquini², Alessandro Gomes Schuffner²

¹ Faculdade Ciências Médicas de Minas Gerais – Belo Horizonte – MG - Brasil
² Conceber -Curitiba - PR- Brasil

Objective: To evaluate whether the administration of Atosiban acetate, a medication originally used to inhibit preterm labor by blocking oxytocin and vasopressin receptors, prior to the embryo transfer of frozen-thawed embryos without genetic analysis has a positive influence on implantation rates.
Methods: A retrospective observational study conducted between June 2022 and May 2025. One or two embryos were transferred in an artificial cycle for endometrial preparation for frozen-thawed embryo transfers. The study included women aged between 19 and 47, with homologous and heterologous oocytes. The inclusion criteria covered the transfer of blastocysts (D5 and D6), embryos with 100% re-expansion after 2 hours of thawing, regardless of embryonic morphology. Exclusion criteria involved transfers on day 3 of development, endometrial thickness <7.0mm, and progesterone 5 days before transfer ≥1.5ng/mL. The study included 242 transfers of frozen-thawed embryos (with and without genetic analysis), divided into 2 sample groups: G1-with Atosiban acetate administration intravenously 30 minutes before the procedure (n=124 transfers) and G2-without Atosiban acetate administration (n=118 transfers). Subsequently, the groups were reorganized according to the criterion of embryo transfer without preimplantation genetic testing (PGT) analysis, into G3-with Atosiban acetate administration intravenously 30 minutes before the procedure (n=33 transfers) and G4-without Atosiban acetate administration (n=48 transfers). The Z test for 2 proportions was then used as the statistical method to compare the implantation rate between groups G1 vs G2 and G3 vs G4, adopting a p<0.05. These data were cross-referenced using patient medical record numbers, maintaining blinding and anonymity.
Results: The analysis of the study shows that the implantation rate for the group that received Atosiban acetate (G1) was 66.1%, while in the group that did not receive the medication, it was 61.8% (G2). Although numerically superior, there was no statistically significant difference, indicating that, overall, Atosiban acetate has no influence on implantation rates. However, with respect to the subgroup of frozen-thawed embryo transfers without preimplantation genetic analysis, a significant difference was revealed. The implantation rate with Atosiban acetate (G3) reached 72.7%, a value relatively higher when compared to the group without the medication (G4), which reached 47.9%. It is important to note that the results may vary according to the patient's profile and the specific conditions of each case.
Conclusion
In frozen-thawed embryo transfers without PGT analysis, Atosiban acetate substantially increased the implantation rate, suggesting that its use may be beneficial in situations of greater uncertainty regarding embryo quality. Nevertheless, in the analyzed sample as a whole, no statistically significant difference was observed in implantation rates in embryo transfers. This must be explained by the fact that uterine contractions resulting from the introduction of foreign bodies, such as the catheter used in the transfer, occur due to an inflammatory response and not solely through the action of oxytocin, as occurs at the end of pregnancy. Thus, the decision to use Atosiban should be personalized and based on a careful medical evaluation.