Time-lapse imaging provides further evidence that planar arrangement of blastomeres is highly abnormal
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Recently, guidelines on the annotation of dynamic human embryo monitoring recommended screening for the presence of planar blastomere arrangement at the 4-cell stage. This observational study was set up in order to analyze whether developmental kinetics of planar human embryos are different from tetrahedral ones.
Therefore, embryos of 115 consecutive ICSI patients (showing 32 planar and 554 tetrahedral embryos) were cultured in a new time-lapse system (Miri TL) and their embryos were annotated for morphokinetic development and screened for irregular cleavages and morphological dysmorphisms.
Significantly less planar embryos reached blastocyst stage and showed worse quality as compared to regular tetrahedral embryos. The rate of bi- and/or multinucleation was also significantly higher in the affected group. Irregular cleavages, particularly embryo rolling, were more often seen in planar embryos. Morphokinetics between planar and tetrahedral were distinguishable up to 4-cell stage (t2–t4), thereafter the observed delay in planar embryos (t8) was more likely the result of a higher rate of arrested embryos in the planar group.
Planar embryos are associated with both a significant increase in irregular cleavage as well as a delay in preimplantation development. This indicates that planar embryos are rather abnormal and should only be considered for transfer if no other embryos are available.
KeywordsPlanar embryos Time-lapse imaging Morphokinetics Multinucleation Irregular cleavage
The authors would like to thank G. Schappacher-Tilp for statistical expertise.
TE: manuscript writing, data management. AH: data collection. PO: data management, manuscript editing. ER: manuscript editing. SHE: data collection. RBM: data collection. EP: protocol development, data analysis. OS: manuscript editing, project development.
Compliance with ethical standards
To ensure objectivity and transparency in research it is stated that no funding was received for this study.
Conflict of interest
None of the authors/coauthors declared a conflict of interest related to this study.
As mentioned in the “Methods” section time-lapse technology in our lab is routinely applied, therefore we refrained from applying for IRB approval for the present observational study.
Patients gave informed consent and were not charged for time-lapse imaging. In no case affected embryos were transferred. No animals were involved.
Video 1. Planar arrangement of cells. It should be noted that oocyte presents 1PN between 14h and 30h before 2Pn formed (35h). t2 (44.8h), t3 (57.8h), and t4 (58.5h) are delayed and embryo development stopped at 6-cell stage (MP4 17760 kb)
Video 2. Regularly fertilized zygote (2Pn) resulting in planar arrangement of cells (43.4h). At 112.6h early morula stage is reached upon which development stopped (MP4 38041 kb)
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