title: A randomized controlled trial comparing two vitrification methods versus slow-freezing for cryopreservation of human cleavage stage embryos.
abstract: OBJECTIVE
  To compare two different vitrification methods to slow freezing method for cryopreservation of human cleavage stage embryos.
  
  
  METHODS
  Prospective randomised trial.
  
  
  METHODS
  University assisted reproduction centre.
  
  
  METHODS
  568 patients (mean age 33.4 ± 5.2) from April 2009 to April 2011.
  
  
  METHODS
  1798 supernumerary good-quality cleavage stage embryos in 645 IVF cycles intended to be cryopreserved were randomly allocated to three groups: slow freezing, vitrification with the Irvine® method, vitrification with the Vitrolife® method.
  
  
  METHODS
  Embryo survival and cleavage rates, implantation rate.
  
  
  RESULTS
  A total of 1055 embryos were warmed, 836 (79.2%) survived and 676 were finally transferred (64.1%). Post-warming embryos survival rate was significantly higher after vitrification (Irvine: 89.4%; Vitrolife: 87.6%) than after slow freezing (63.8%) (p < 0.001). No differences in survival rates were observed between the two vitrification methods, but a significant higher cleavage rate was observed using Irvine compared to Vitrolife method (p < 0.05). Implantation rate (IR) per embryo replaced and per embryo warmed were respectively 15.8% (41/259) and 12.4% (41/330) for Irvine, 17.0% (40/235) and 12.1% (40/330) for Vitrolife, 21.4% (39/182) and 9.9% (39/395) for slow-freezing (NS).
  
  
  CONCLUSIONS
  Both vitrification methods (Irvine and Vitrolife) are more efficient than slow freezing for cryopreservation of human cleavage stage embryos in terms of post-warming survival rate. No significant difference in the implantation rate was observed between the three cryopreservation methods.
authors: Research Laboratory on Human Reproduction, Faculty of Medicine, Université Libre de Bruxelles, Campus Erasme, Bruxelles, Belgium, Giovanna.Fasano@erasme.ulb.ac.be.
authors: Giovanna
authors: G
authors: Fasano
authors: Nicolas
authors: N
authors: Fontenelle
authors: Anne-Sophie
authors: AS
authors: Vannin
authors: Jamila
authors: J
authors: Biramane
authors: Fabienne
authors: F
authors: Devreker
authors: Yvon
authors: Y
authors: Englert
authors: Anne
authors: A
authors: Delbaere
mesh_terms: D000328:Adult; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation / Q000379:methods*; D010064:Embryo Implantation; D005260:Female; D005307:Fertilization in Vitro; D005615:Freezing; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D015996:Survival Rate; D058989:Vitrification