JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):227
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263854

P-215. Success Rate of Frozen-Thawed Embryo Transfer hatched blastocyst

Andrea Mesquita Lima¹, Gleicyane Sousa Santos Alam¹, Renata Reis Pimentel Castro¹, Sebastiao Evangelista Torquato Filho¹, Fábio Eugênio Magalhães Rodrigues¹, Tulius Augustus Ferreira Freitas¹, Marcus Aurelio Bessa Paiva¹, Ellayne Cavalcanti Queiroz¹, Eduardo Gomes Sá¹

¹ Bios Centro de Medicina Reprodutiva – Fortaleza -CE -Brasil

Objective: Frozen-thawed embryo transfer is a common practice in assisted reproduction techniques, especially in in vitro fertilization (IVF). The process of freezing and thawing embryos is crucial for preserving embryo viability. However, a phenomenon that has received attention is the presence of embryos that, after thawing, are not in the zona pellucida. The zona pellucida is a protective structure surrounding the embryo, and its integrity is considered important for embryonic development and implantation. This study aims to investigate the success rate of frozen-thawed embryo transfer that is outside the zona pellucida, analyzing the implications for reproductive outcomes.
Methods: A retrospective study was conducted with 350 patients who underwent frozen-thawed embryo transfers between January 2020 and December 2023 at an assisted reproduction clinic. Patients were divided into two groups: Group A (embryos thawed within the zona pellucida) and Group B (embryos thawed outside the zona pellucida). Demographic characteristics of the patients, such as age, BMI, and reproductive history, were recorded. Clinical pregnancy rates were assessed, defined as the presence of a fetal heartbeat on ultrasound. Rates of spontaneous abortion, gestational development, and obstetric complications were also analyzed. Significant differences were considered at p<0.05.
Results: The results showed that the clinical pregnancy rate was significantly lower in Group B (outside the zona pellucida), at 25%, compared to Group A, which had a rate of 45% (p<0.01). In addition, the spontaneous abortion rate was higher in Group B, at 30%, compared to 15% in Group A (p<0.05).
Conclusion: The zona pellucida not only protects the embryo during early development, but also appears to be involved in communication between the embryo and the endometrium, facilitating implantation. The absence of this structure may compromise the embryo's ability to implant properly and develop healthily. Previous studies corroborate these observations, indicating that embryos without the zona pellucida may have difficulty interacting with the endometrium, resulting in reduced pregnancy rates.