Using strict criteria to select potentially viable blastocysts is crucial to success:

  • Growth rate: expanded blastocyst stage on Day 5/ Day 6.
  • Overall cell number >60 cells (depending on day of development).
  • Relative cell allocation to trophectoderm/inner cell mass.
  • Original quality of early stage embryo: pronucleus formation and orientation, blastomere regularity, mono-nucleation, fragmentation, appropriate cleavage stage for time of development.