JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):56
Poster Presentation
29th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263595
P-44. Comparison Between Buffered and Non-Buffered Media in Embryo Transfer
Jonathan Boncristiano1, Bernardo Rodrigues Moura2, Emilio Costa Garavini3, Frederico Augusto Souza Freitas3, Natália Reis Souza2, Isabella Oliveira Macedo4, João Pedro Alves Freitas2, Carolina Pinhol Vieira5
1 Gerar In Vitro - Vitoria da Conquista - BA - Brasil
2 Gerar In Vitro - Belo Horizonte - MG - Brasil
3 Gerar In Vitro - Ponte Nova - MG - Brasil
4 Gerar In Vitro - Itabuna - BA - Brasil
5 Gerar In Vitro - Montes Claros - MG - Brasil
Objective: To compare outcomes between IVF cycles differing only in the embryo transfer medium (HEPES-buffered vs bicarbonate-buffered), with identical culture conditions; positive β-hCG and clinical pregnancy were analyzed overall and by age.
Methods: A retrospective study involving patients who underwent IVF cycles between January 2021 and December 2024. The data were divided into two groups according to the culture medium used for catheter flushing and the embryo transfer drop: HEPES-buffered medium (B group), which does not require stabilization in an incubator; and Global® bicarbonate-buffered medium (NB group), pre-stabilized in an incubator to maintain a pH between 7.27 and 7.30. All other laboratory procedures — including gamete handling and embryo culture — were standardized and did not vary in this study. Patients undergoing embryo transfer at the cleavage or blastocyst stage, with fresh or frozen embryos, were included. Cycles involving egg donation, biopsied embryos, or those canceled before transfer were excluded. Patients were stratified by age: <35 years, 35–39 years, 40–42 years, and >42 years. The evaluated outcomes were the positive β-hCG rate (measured 10–12 days after transfer) and the clinical pregnancy rate, defined as the presence of a gestational sac with a heartbeat on transvaginal ultrasound. Comparisons between groups, and between age-stratified subgroups, were performed using the chi-square test, with p<0.05 considered statistically significant.
Results: In the overall analysis, the Buffered Group showed a significantly higher positive β-hCG rate (44.8%, n=995; Non-buffered Group: 34.5%, n=985; p<0.001). The clinical pregnancy rate was also higher in the Buffered Group (31.2%, n=956; Non-buffered Group: 25.8%, n=848; p=0.012). In the age-stratified analysis, the Buffered Group showed a higher tendency in clinical pregnancy rates across all subgroups, although differences were not statistically significant. Among patients under 35 years old, rates were 33.8% (n=400; Non-buffered: 30.5%, n=341; p=0.345). In the 35–39 years group, rates were 57.8% (n=598; Non-buffered: 42.2%, n=288; p=0.078). For patients aged 40–42 years, rates were 24.8% (n=113; Non-buffered: 17.4%, n=92; p=0.200). Among those over 42 years, rates were 24.6% (n=69; Non-buffered: 13.6%, n=59; p=0.115). Despite the lack of statistical significance in these comparisons, there was a consistent trend toward better clinical outcomes with the use of buffered medium.
Conclusion: The comparison between HEPES-buffered medium and Global® bicarbonate-buffered medium used during embryo transfer revealed a statistically significant difference in positive β-hCG and clinical pregnancy rates in the overall analysis. This difference did not appear to be influenced by patient age, as no statistically significant variations were observed in the age-stratified comparisons. These findings suggest that the use of HEPES-buffered medium during embryo transfer may have a more positive impact on clinical outcomes, regardless of age group.