JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):34
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263558

P-22. Association between blastocoel expansion grade and clinical pregnancy rate in single euploid embryo transfers

Bianca Thais de Paula¹, Patricia Pinho França¹, Carolina Pinhol Vieira², Inês Katerina Damasceno Cavallo Cruzeiro¹

¹ Clinica LifeSearch FertGroup - Belo Horizonte - MG - Brasil
² Universidade Federal de Minas Gerais - Belo Horizonte - MG - Brasil

Objective: Blastocoel expansion grade is part of the blastocyst morphological assessment, and recent guidelines recommend prioritizing higher grades (G; G4-G6) for transfer. This study aimed to evaluate whether blastocoel expansion grade is associated with differences in clinical pregnancy rate (β-hCG positive) in single euploid embryo transfers (SET).
Methods: This retrospective study included 78 patients undergoing 93 SETs of euploid embryos (trophectoderm and/or inner cell mass grades A or B) between Feb/2024 and Jun/2025 (mean age at oocyte retrieval: 37.5 years, range 29–44). Blastocysts were graded for blastocoel expansion according to Gardner & Schoolcraft (G3, G4, G5) at least 2h after thawing. Were excluded from the study embryos with grades 2 (n=3), 6 (n=4) or inadequate re-expansion, and embryos with TE/ICM grade C (n=6). All patients had endometrium ≥7 mm at progesterone start. Endometrial preparation was mainly natural cycle or with oral estrogen, followed by standard vaginal progesterone, with some cases supplemented orally. Data normality was assessed by D’Agostino–Pearson and Shapiro–Wilk tests, and statistical comparisons made using Kruskal–Wallis (p<0.05). Analyses performed: comparisons between blastocoel expansion grades (G3, G4, G5) in the following groups:
1. Total sample;
2. Excluding patients with ≥2 SETs;
3. Day 5 blastocysts only;
4. Day 5 blastocyst only, excluding patients with ≥2 SETs;
5. TE grade A;
6. TE grade A, day 5 blastocyst only;
7. TE grade A without repeated patients
8. TE grade A without repeated patients, day 5 blastocyst only.
Results: No statistically significant differences in clinical pregnancy rates were observed (mean±SD).
1. Total sample: G3 0.64±0.48 (n=25), G4 0.61±0.49 (n=21), G5 0.70±0.46 (n=34), p=0.7735.
2. Excluding multiple SET patients: G3 0.72±0.46 (n=18), G4 0.69±0.48 (n=13), G5 0.80±0.40 (n=25), p=0.7310.
3. Day 5 only: G3 0.55±0.51 (n=20), G4 0.61±0.50 (n=18), G5 0.75±0.44 (n=28), p=0.3329.
4. Day 5 only, no repeated patients: G3 0.61±0.50 (n=13), G4 0.66±0.49 (n=12), G5 0.82±0.38 (n=23), p=0.3433.
5. TE grade A: G3 0.56±0.51 (n=16), G4 0.53±0.51 (n=15), G5 0.80±0.40 (n=25), p=0.1446.
6. TE grade A, Day 5 only: G3 0.50±0.51 (n=14), G4 0.50±0.51 (n=14), G5 0.82±0.38 (n=23), p=0.0560.
7. TE grade A, no repeated patients: G3 0.63±0.50 (n=11), G4 0.63±0.50 (n=11), G5 0.89±0.31 (n=19), p=0.1653.
8. TE grade A, Day 5 only, no repeated patients: G3 0.55±0.52 (n=9), G4 0.60±0.51 (n=10), G5 0.89±0.31 (n=19), p=0.0905.
Conclusion: Although statistical significance was not reached, a trend toward higher clinical pregnancy rates was observed for G5 euploid blastocysts, particularly in day 5 transfers and when TE grade A was present. This result reinforces that the embryo quality and the blastocoel expansion impacts on the treatment success and suggests that Day 5 embryos may have a greater chance of pregnancy. However, larger prospective studies, with implantation rate as the primary outcome, are ongoing to confirm these findings and assess the prognostic value of blastocoel expansion grade in single euploid embryo transfers (SET).