JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):102
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263689

P-90. Excluded Cell Morulae: Are They Really Low-Quality Embryos? Insights from Euploidy and Fragmentation Analysis in a Time-Lapse Cohort

Marcus Aurélio Paiva Bessa, Hamilton de Martin, Eduardo Gomes Sá, Ellayne Cavalcanti Queiroz, Andrea Mesquita Lima, Gleicyane Sousa Santos Alam, Renata Reis Pimentel Castro, Tulius Augustus Ferreira Freitas, Eduardo Paula Miranda, Sebastião Evangelista Torquato

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

Objective: Blastocysts originating from partially compacted morulae with excluded cells (Exc PCM) are commonly categorized as low-quality embryos based on static morphological and morphokinetic assessments. However, whether this classification is justified by chromosomal constitution or by inner cell mass/trophectoderm (ICM/TE) fragmentation remains uncertain. This study aimed to determine whether Exc PCM embryos are truly disadvantaged in terms of euploidy and fragmentation rates compared to fully compacted morulae (FCM) and those with extruded cells (Ext PCM), and to evaluate the predictive value of morula compaction relative to conventional embryo scoring systems.
Methods: This retrospective cohort study analysed 1,182 embryos individually cultured in time-lapse incubators (EmbryoScope Plus, Vitrolife) and biopsied for preimplantation genetic testing for aneuploidy (PGT-A) between September 2022 and December 2024. Morulae were classified into three groups: fully compacted (FCM), partially compacted with excluded cells (Exc PCM), and partially compacted with extruded cells (Ext PCM). Embryos were further stratified by Gardner morphological grade (A=AA, AB, BA; B=BB, BC, AC; C=CA,CB,CC), KIDScore (A: >7; B: 4–7; C: <4), and ICM/ TE fragmentation (Blastocyst Fragmentation Indicator – BFI: NN, FN, FF). Euploidy and fragmentation rates were compared among groups using contingency tables and chi-square tests. Predictive value for euploidy was estimated using logistic regression, with odds ratios (OR) and 95% confidence intervals (CI), and area under the ROC curve (AUC) was calculated to assess discriminatory capacity.
Results: Among 1,182 embryos analysed, 871 (73.7%) were FCM, 224 (19.0%) Exc PCM, and 87 (7.4%) Ext PCM. Euploidy rates were similar between FCM (46.8%) and Exc PCM (45.5%) but significantly reduced in Ext PCM (18.4%) (p<0.001). Logistic regression confirmed Ext PCM as an independent predictor of aneuploidy (OR=0.26; 95% CI: 0.15–0.45; p<0.001 vs FCM), while Exc PCM did not differ significantly from FCM (OR=0.95; 95% CI: 0.71–1.27; p=0.73). Exc PCM embryos were disproportionately assigned lower morphological grades (Gardner: A 20.1%, B 40.2%, C 39.7%) and lower KIDScore categories (A 7.1%, B 38.4%, C 54.5%) compared to FCM (Gardner: A 62.7%, KIDScore A 47.8%). Nonetheless, their euploidy rates remained similar to FCM and notably superior to Ext PCM. ICM/TE fragmentation analysis (BFI) showed that most Exc PCM embryos were classified as NN (no fragmentation: 54.9%) or FN (fragmentation restricted to ICM: 22.8%), with only 22.3% showing full ICM/TE fragmentation (FF). In contrast, Ext PCM displayed a markedly higher prevalence of FF (57.5%). The overall predictive performance of morula compaction for euploidy was modest (AUC=0.54), indicating limited discriminatory capacity when used in isolation. Subgroup analyses revealed that the presence of excluded cells alone was not associated with increased aneuploidy or higher rates of ICM/TE fragmentation, challenging the practice of systematically deprioritizing these embryos in clinical selection.
Conclusion: Although Exc PCM embryos are consistently assigned lower morphological and morphokinetic scores compared to fully compacted morulae, their rates of euploidy and ICM/TE fragmentation are equivalent. In contrast, Ext PCM embryos exhibit both poor grading and high rates of aneuploidy and fragmentation. The presence of excluded cells per se is not predictive of chromosomal abnormalities or increased blastocyst fragmentation. These findings suggest that the widespread bias against Exc PCM embryos in embryo selection is unwarranted, and that clinical deselection should not be based solely on this parameter. This analysis represents a focused segment of a larger, ongoing investigation using the same time-lapse embryo cohort, with additional morphodynamic parameters being addressed in parallel studies.