title: Outcome of cryotransfer of embryos developed from vitrified oocytes: double vitrification has no impact on delivery rates.
abstract: OBJECTIVE
  Evaluate the outcome of cryotransfer of embryos developed from vitrified oocytes.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Private university-affiliated IVF center.
  
  
  METHODS
  Women undergoing warming cycles in which vitrified embryos were developed from vitrified or fresh oocytes.
  
  
  METHODS
  Vitrification by the Cryotop open device.
  
  
  METHODS
  Delivery rate (DR) per warming cycle.
  
  
  RESULTS
  A total of 471 warming cycles of 796 vitrified embryos developed from vitrified oocytes (group 1) and 2,629 warming cycles of 4,394 vitrified embryos derived from fresh oocytes (group 2) were evaluated. Overall survival rates were 97.2% [95% confidence interval [CI] 95.9%-98.6%] vs. 95.7% [95% CI 94.9-96.4], respectively. DRs per warming cycle were 33.8% (group 1) and 30.9% (group 2). Double vitrification had no effect on DR (odds ratio [OR] 0.877, 95% CI 0.712-1.080). Confounding factors (ovum donation or autologous cycles; day-3 or blastocyst embryo transfer [ET]; natural or hormonal replacement therapy for ET; single or double ET; previous cycles, number of oocytes, doses of gonadotropins and E2 levels on the day of hCG) did not modify the effect of double vitrification on DR (OR 0.872, 95% CI 0.702-1.084).
  
  
  CONCLUSIONS
  Vitrification at early cleavage or blastocyst stage of embryos obtained from previously vitrified oocytes has no effect on DR/warming cycle.
authors: IVI-Valencia, Institut Universitari IVI, Valencia, Spain. ana.cobo@ivi.es
authors: Ana
authors: A
authors: Cobo
authors: Damià
authors: D
authors: Castellò
authors: Begoña
authors: B
authors: Vallejo
authors: Carmela
authors: C
authors: Albert
authors: José María
authors: JM
authors: de los Santos
authors: José
authors: J
authors: Remohí
mesh_terms: D000328:Adult; D002470:Cell Survival / Q000502:physiology; D015331:Cohort Studies; D015925:Cryopreservation / Q000379:methods* / Q000639:trends; D004624:Embryo Transfer / Q000379:methods* / Q000639:trends; D005260:Female; D006801:Humans; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D018873:Pregnancy Rate / Q000639:trends; D012189:Retrospective Studies; D058989:Vitrification