title: There is a cutoff limit in diameter between a blastomere and a small anucleate fragment.
abstract: OBJECTIVE
  To document the DNA content of blastomeres/fragments from early human preembryos and to determine if there is a "cutoff" diameter at which a cell should be considered an anucleate fragment rather than a blastomere.
  
  
  METHODS
  Surplus embryos from in vitro fertilization were used. Individual cells were measured, fixated, and stained for DNA.
  
  
  RESULTS
  In day 2 preembryos, only 2% of cells with a diameter <45 microm contained DNA, compared with 67% of those > or =45 microm. In day 3 preembryos, 3% of cells <40 microm contained DNA, compared with 66% of those > or =40 microm.
  
  
  CONCLUSIONS
  It is suggested that cells <45 microm in day 2 preembryos, and <40 microm in day 3 preembryos should be classified as fragments, and cells larger than this, as blastomeres. This may influence the embryo scoring system for in vitro fertilization. We therefore recommend that cells within this critical range should be measured when scoring preembryos for embryo transfer.
authors.affiliation: IVF-Laboratory, Unit of Reproductive Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden. maria.in.johansson@vgregionen.se
authors.forename: Maria
authors.initials: M
authors.lastname: Johansson
authors.forename: Thorir
authors.initials: T
authors.lastname: Hardarson
authors.forename: Kersti
authors.initials: K
authors.lastname: Lundin
mesh_terms: D001755:Blastocyst / Q000166:cytology* / Q000378:metabolism; D001757:Blastomeres / Q000166:cytology* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D005260:Female; D006801:Humans
chemical_list: D004247:DNA