Time-lapse imaging provides further evidence that planar arrangement of blastomeres is highly abnormal

Purpose 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. Methods 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. Results 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. Conclusions 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.