P-287 Characterization of novel blastocyst development parameters using Time-Lapse Imaging: insights into embryo hyperactivity and its putative impact on embryo selection

Abstract Study question Can novel Time-Lapse imaging behaviour, such as embryo hyperactivity, provide valuable insights for improving embryo selection and predicting blastocyst developmental outcomes? Summary answer Embryo hyperactivity (HE) does not compromise the in-vitro development to the blastocyst stage, and is not correlated with direct cleavage, nor morphokinetic parameters timings. What is known already Embryonic hyperactivity is a novel but underexplored phenomenon observed through Time-Lapse Imaging. Unlike extensively studied morphokinetic events like multinucleation and direct cleavage, hyperactivity involves rapid, irregular, and spasmodic movements of the fertilized oocyte, persisting through cleavage stages to blastocyst formation. The literature lacks a standardized definition and clear biological significance, leaving its impact on embryo development and implantation uncertain. Limited research hinders classification and clinical interpretation. While advanced imaging enables its detection, further studies are needed to assess its relevance in assisted reproduction and its potential as an indicator of embryo quality and developmental competence. Study design, size, duration This retrospective study, conducted at two private Reproductive Medicine Centers (April–September 2024), analyzed 748 blastocysts from 175 ICSI cycles (2022–2024) using Time-Lapse imaging. The study aimed to assess novel developmental parameters, focusing on cytoplasmic hyperactivity and its potential impact on blastocyst quality and embryo selection in Assisted Reproductive Technology (ART). Participants/materials, setting, methods This study included only blastocysts from ICSI cycles, excluding conventional IVF cases. Developmental parameters analyzed included pronuclear formation, cleavage stages (t2–t8), direct cleavage (DC), morula formation, blastulation onset, and blastocyst collapse. Unfertilized oocytes were observed for hyperactivity. Blastocysts with incomplete Time-Lapse imaging were excluded. Statistical analyses, including logistic regression and a linear mixed model, were performed using STATA 18.1. Comparisons were made between hyperactive and non-hyperactive embryos, with significance set at p < 0.05. Main results and the role of chance In this study, we analyzed 748 embryos from 175 ICSI cycles to assess embryonic hyperactivity, defined as abrupt, atypical movements within embryonic cells. Among them, 411 embryos (54.95%) reached the blastocyst stage. Direct cleavage (DC) was observed in 185 blastocysts (48.3%), occurring on average at 40 ± 9 hours post-fertilization. Hyperactivity was identified in 118 embryos (15.8%), with an average duration of 30 hours (range: 0.83–136.33 hours). Of these, 73 hyperactive embryos (17.76%) reached the blastocyst stage, while 45 did not (13.35%). Additionally, 57 hyperactive embryos exhibited DC, and 33 of them reached the blastocyst stage. In contrast, 338 of the 411 blastocysts (82.24%) showed no hyperactivity. Statistical analyses (Mann–Whitney test) revealed no significant difference in blastocyst formation rates between hyperactive and non-hyperactive embryos (p > 0.05). Further analysis explored associations between hyperactivity and other embryo characteristics, including DC, blastocyst collapse, and morphokinetic parameters. A linear mixed model accounting for embryo origin showed no significant correlation between hyperactivity and developmental timings (e.g., pronuclear appearance, syngamy, cleavage stages, morula, blastocyst formation, cytoplasmic waves, DC, or collapse) (p > 0.05). These findings suggest that hyperactivity is not predictive of blastocyst formation or other morphokinetic parameters. Limitations, reasons for caution This study’s small sample size may limit the detection of correlations between hyperactivity and embryonic traits. The variability in hyperactivity duration raises questions about its impact on development. Further research should explore its relationship with compaction, blastocoel formation, and zona pellucida integrity to refine its characterization and developmental significance Wider implications of the findings This study provides novel insights into embryonic hyperactivity, a previously underexplored phenomenon. Despite no observed correlations with standard morphokinetic parameters, its characterization expands our understanding of dynamic embryonic behaviors. Future research may clarify its role in embryo viability, implantation potential, and its implications for ART Trial registration number No