title: The neglected morula/compact stage embryo transfer.
abstract: BACKGROUND
  This retrospective study analysed the outcomes of 339 embryo transfers on either day 3 (n = 97) or day 4 (n = 242), and proposed a grading system for morula/compact embryos.
  
  
  METHODS
  The morula/compact embryo grading was based on: (i) the proportion of blastomeres undergoing the compaction process; (ii) the morphology of the compacted multicellular mass; (iii) the embryo quality on day 2 and 3; and (iv) the amount of fragmentation. Embryo transfers were classified into groups as follows: group I: transferred with zero 'good' embryos; group II: one 'good' embryo; group III: two or more 'good' embryos.
  
  
  RESULTS
  Patients on day 4 were transferred with significantly fewer embryos in groups II and III (2.58 +/- 0.9 and 2.35 +/- 0.6 respectively) when compared with the correspondent day 3 transfers (3.81 +/- 1.4 and 4.07 +/- 0.9 respectively) (P < 0.05), but had the same or higher implantation and pregnancy rates. Analysing the patients who had transfers with all 'good' embryos, day 4 transfer achieved a significantly higher implantation rate compared with day 3 transfer (46.4 versus 21.4%, P < 0.01), but the number of embryos transferred on day 4 was significantly lower than day 3 (2.1 +/- 0.5 versus 3.5 +/- 0.9, P < 0.01).
  
  
  CONCLUSIONS
  The morula/compact embryos had great value for embryo selection, which significantly reduced the number of embryos needed for transfer.
authors.affiliation: Arizona Institute of Reproductive Medicine, Phoenix, Arizona, USA. jtftc@aol.com
authors.forename: Jun
authors.initials: J
authors.lastname: Tao
authors.forename: Robert
authors.initials: R
authors.lastname: Tamis
authors.forename: Katharine
authors.initials: K
authors.lastname: Fink
authors.forename: Brenda
authors.initials: B
authors.lastname: Williams
authors.forename: Tresa
authors.initials: T
authors.lastname: Nelson-White
authors.forename: Randall
authors.initials: R
authors.lastname: Craig
mesh_terms: D000328:Adult; D001757:Blastomeres / Q000166:cytology; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D009028:Morula / Q000166:cytology*; D011247:Pregnancy; D012189:Retrospective Studies; D013997:Time Factors