title: Nuclear status of four-cell preembryos predicts implantation potential in in vitro fertilization treatment cycles.
abstract: OBJECTIVE
  To assess the value of routine screening of nuclear status of day-2 four-cell preembryos for single embryo transfer (SET) in predicting implantation.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  Private IVF unit.
  
  
  METHODS
  A total of 1,985 fresh embryo transfers on day 2 or day 3 were performed from January 2002 to November 2004. In 1,295 (65.2%) of these transfers, SET was performed. All day-2 four-cell preembryos transferred in SET cycles (n = 861) were analyzed retrospectively for outcome in terms of implantation rate and its relation to the number of visible mononucleate blastomeres (MNBs), the degree of fragmentation, and equality of blastomeres.
  
  
  METHODS
  Light microscopic evaluation of preembryos before transfer on day 2.
  
  
  METHODS
  Implantation rate.
  
  
  RESULTS
  The number of MNBs was found to be related to implantation, whereas blastomere equality and rate of embryo fragmentation were not. The implantation rate was statistically significantly higher in cycles where a four-cell preembryo with four MNBs was transferred than after transfer of a four-cell preembryo with zero to three MNBs (42% versus 22%). In a logistic regression analysis, nucleation of all blastomeres was the only morphologic parameter that was associated with the implantation rate.
  
  
  CONCLUSIONS
  Evaluation of nuclear status of four-cell preembryos is important in predicting implantation potential. Visualization of four MNBs in a four-cell preembryo predicted a statistically significant higher implantation rate than in cases where not all four blastomeres were mononucleate.
authors.affiliation: IVF Clinic CURA, Malmö, Sweden. pia.saldeen@curakliniken.se
authors.forename: Pia
authors.initials: P
authors.lastname: Saldeen
authors.forename: Per
authors.initials: P
authors.lastname: Sundström
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000166:cytology* / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology*; D010064:Embryo Implantation / Q000502:physiology*; D004624:Embryo Transfer / Q000706:statistics & numerical data; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D016896:Treatment Outcome