title: Embryo cryopreservation at the pronuclear stage and efficient embryo use optimizes the chance for a liveborn infant from a single oocyte retrieval.
abstract: OBJECTIVE
  To estimate the potential for a liveborn in our program achieved through either fresh or frozen embryos derived from a single oocyte retrieval.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  A tertiary referral reproductive medicine unit.
  
  
  METHODS
  All consecutive patients undergoing oocyte retrieval from January 1, 1996, to June 30, 1997.
  
  
  METHODS
  All couples undergoing IVF-ET at our center are counseled about a specific embryo transfer number after oocyte retrieval based on demographic and historical factors. Only this specified number of embryos is retained in culture. All normally fertilized (2PN) oocytes exceeding this number are immediately cryopreserved at the pronuclear stage. For couples who do not conceive after fresh embryo transfers, frozen embryo transfers are subsequently performed by usually thawing only the number of embryos intended for transfer, thereby conserving remaining embryos for further potential frozen embryo cycles.
  
  
  METHODS
  Liveborn delivery per oocyte retrieval.39.0 years were 61.2%, 59.7%, and 18.5%, respectively.
  
  
  CONCLUSIONS
  For women <39 years of age, the efficient use of embryo cryopreservation at the pronuclear stage and economical embryo utilization policies results in cumulative chances for a liveborn exceeding 60%.
authors.affiliation: Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Damario
authors.forename: D G
authors.initials: DG
authors.lastname: Hammitt
authors.forename: D R
authors.initials: DR
authors.lastname: Session
authors.forename: D A
authors.initials: DA
authors.lastname: Dumesic
mesh_terms: D000328:Adult; D001723:Birth Rate; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007246:Infertility / Q000628:therapy; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D011272:Pregnancy, Multiple; D012099:Reproductive Techniques; D012189:Retrospective Studies