title: Cryopreservation of day 2-3 embryos by vitrification yields better outcome than slow freezing.
abstract: OBJECTIVE
  To compare the outcome of vitrification versus slow freezing cryopreservation for cleavage stage day 2-3 embryos.
  
  
  METHODS
  A retrospective observational study.
  
  
  METHODS
  All thawed embryos assisted reproduction cycles between January 2010 and December 2012 at a single IVF laboratory of a Tertiary Medical Center.
  
  
  METHODS
  Five hundred and thirty-nine cycles of day 2-3 thawed embryos.
  
  
  METHODS
  In 327 of the thawed cycles, the embryos were vitrified and in 212 of the cycles the embryos were derived from slow freezing embryos.
  
  
  METHODS
  Embryo survival rate, blastomere surviving rate and pregnancy rate.
  
  
  RESULTS
  Embryo survival rate was significantly higher after vitrification compared with slow freezing (81.6%, 647/793 versus 70.0%, 393/562 embryos, p < 0.0001). The clinical pregnancy rate per ET was significantly higher following vitrification compared to slow freezing, 20.0%, 63/314 versus 11.9%, 23/193, respectively (p = 0.02).
  
  
  CONCLUSIONS
  Vitrification of day 2-3 cleavage stage embryos yields better cycle outcome in all the parameters compared to slow freezing.
authors.affiliation: Department of Obstetrics and Gynecology, IVF Unit, The Chaim Sheba Medical Center, Tel Hashomer, Ramat Gan, Israel; affiliated to Sackler School of Medicine, Tel Aviv University , Tel Aviv , Israel.
authors.forename: Jacob
authors.initials: J
authors.lastname: Levron
authors.forename: Oshrit
authors.initials: O
authors.lastname: Leibovitz
authors.forename: Masha
authors.initials: M
authors.lastname: Brengauz
authors.forename: Hila
authors.initials: H
authors.lastname: Gitman
authors.forename: Gil M
authors.initials: GM
authors.lastname: Yerushalmi
authors.forename: Eldad
authors.initials: E
authors.lastname: Katorza
authors.forename: Itai
authors.initials: I
authors.lastname: Gat
authors.forename: Shai E
authors.initials: SE
authors.lastname: Elizur
mesh_terms: D000328:Adult; D001757:Blastomeres; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation / Q000379:methods*; D004477:Ectogenesis; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D004622:Embryo, Mammalian; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007247:Infertility, Female / Q000628:therapy*; D007557:Israel / Q000453:epidemiology; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors; D014022:Tissue Survival; D058989:Vitrification