JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):107
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263723

P-95. Fast, Slow, Steady: What Embryo Speed Tells Us about Chromosomal Status – Insights from Morphokinetics Trajectories of 11,915 Biopsied Blastocysts

Aline Rodrigues Lorenzon¹, Andreu Quintana-Vechí², Erkan Kalafat³, Irene Miguel-Escalada², Dóris Spinosa Chéles¹, Mauricio Barbour Chehin¹, José Roberto Alegretti¹, Mina Popovic⁴

¹ Huntington Medicina Reprodutiva - Eugin Group - São Paulo - SP – Brasil
² EUGIN BARCELONA, Spain
³ KOÇ UNIVERSITY HOSPITAL INSTANBUL, Turkey ⁴ GHENT UNIVERSITY HOSPITAL, Belgium

Objective: Time-lapse monitoring offers detailed insights of embryo development, providing opportunities for non-invasive selection in IVF. While preimplantation genetic testing for aneuploidy (PGT-A) is the gold standard for assessing chromosomal status, it remains costly, invasive, and not universally accessible. This study aimed to define reproducible developmental trajectory profiles from fertilization to blastocyst formation using morphokinetic data, and to evaluate their association with euploidy rates, independent of maternal age and blastocyst morphology. The ultimate goal was to assess their potential as a non-invasive selection tool when PGT-A is unavailable or to guide embryo prioritization for biopsy.
Methods: This retrospective multicenter study analyzed 11,915 blastocysts from 3,044 IVF/PGT-A cycles performed between January 2019 and July 2024 in four international fertility clinics across two continents, including 2,917 autologous patients. Embryos were cultured in time-lapse incubators (EmbryoScope Plus^®, Vitrolife) and annotated for key developmental events relative to ICSI (t0): pronuclear fading (tPNf), cleavage divisions (t2–t8), start of blastulation (tSB), and full blastocyst formation (tB). Developmental trajectories were identified via k-means clustering, and associations with euploidy were tested using mixed-effects logistic regression adjusted for maternal age and Gardner's morphological grading. Statistical significance was set at p<0.05.
Results: Mean maternal age was 38.9±3.9 years, and the overall euploidy rate was 40.1%. Aneuploid embryos exhibited slower progression across all preimplantation stages (t2–tB) compared to euploid embryos, with delays increasing toward blastulation: +1.29 h at t8, +2.44 h at tSB, and +3.66 h at tB (all p<0.001). Developmental impact varied by abnormality type: chromosomal gains, including viable trisomies, developed at similar rates to euploid embryos, whereas single and double chromosomal losses produced severity-dependent delays starting from t4 (+3.5 h and +5.5 h to tB, respectively; both p<0.001). Multiple aneuploidies were delayed at all checkpoints (p<0.05). Four distinct developmental trajectories were identified: 1) Consistently rapid – early cleavage and faster progression to blastocyst; 2) Steady – consistent development at average timing; 3) Inconsistent – rapid early cleavage followed by later delays; 4) Consistently delayed – slower progression from the first cleavage onward. Euploidy rates differed significantly among the profiles (p<0.001): rapid (50.4%), steady (41.6%), inconsistent (38.7%), and delayed (31.8%). Compared to delayed embryos, rapid embryos had 1.82-fold higher odds of being euploid (OR=1.82; 95% CI: 1.59–2.08; p<0.001), and steady embryos had 1.41-fold higher odds (OR=1.41; 95% CI: 1.26–1.58; p<0.001). Chromosomal gains were evenly distributed across all trajectories (p>0.05), whereas single and multiple chromosomal losses were significantly enriched in delayed and inconsistent profiles (p<0.001). Multiple abnormalities were associated with the slowest progression.
Conclusion: This large multicenter study identified four reproducible morphokinetic developmental trajectories that are independently associated with euploidy rates, even after adjusting for maternal age and morphology. Consistently rapid and steady developmental patterns showed significantly higher euploidy rates, while delayed and inconsistent profiles were linked to higher rates of chromosomal loss. While these associations could help refine embryo selection algorithms and assist in prioritizing embryos for biopsy when PGT-A is not performed, morphokinetic data alone cannot detect all forms of aneuploidy—particularly chromosomal gains. Further prospective studies are warranted to evaluate its predictive value for implantation and live birth outcomes.