title: Improved human oocyte development after vitrification: a comparison of thawing methods.
abstract: OBJECTIVE
  To evaluate the developmental competence of vitrified human oocytes thawed using two different methods to establish an effective cryopreservation protocol.
  
  
  METHODS
  In vitro model study.
  
  
  METHODS
  University-affiliated hospital.
  
  
  METHODS
  Patients who underwent a long protocol of ovarian stimulation with GnRH and gonadotropins.
  
  
  METHODS
  Vitrified oocytes from the patients were thawed using either a four-step method with 2.5-minute intervals or a four-step method with 5-minute intervals.
  
  
  METHODS
  Morphologic normality, maturation, fertilization, and development of the oocytes to the blastocyst stage.
  
  
  RESULTS
  The two thawing methods did not significantly affect the morphologic normality (84%-100%), maturation (75%-100%), fertilization (38%-71%), polyspermy (more than three pronuclei; 0%-20%), or parthenogenetic activation (only female pronucleus; 0%-8%) of the vitrified oocytes. However, more of the vitrified oocytes developed to the two-cell (71%-100% versus 50%-67%), four-cell (71%-93% versus 0%-50%), eight-cell (46%-71% versus 0%), and blastocyst (23%-36% versus 0%) stages after thawing using the four-step method with 2.5-minute intervals than using the four-step method with 5-minute intervals.
  
  
  CONCLUSIONS
  Vitrified human oocytes developed to the blastocyst stage with IVF. A four-step thawing method with 2.5-minute intervals was more effective in supporting preimplantation embryo development than a four-step thawing method with 5-minute intervals.
authors.affiliation: College of Medicine, Pochon CHA University, Infertility Medical Center of CHA General Hospital, Seoul, South Korea.
authors.forename: S W
authors.initials: SW
authors.lastname: Hong
authors.forename: H M
authors.initials: HM
authors.lastname: Chung
authors.forename: J M
authors.initials: JM
authors.lastname: Lim
authors.forename: J J
authors.initials: JJ
authors.lastname: Ko
authors.forename: T K
authors.initials: TK
authors.lastname: Yoon
authors.forename: B
authors.initials: B
authors.lastname: Yee
authors.forename: K Y
authors.initials: KY
authors.lastname: Cha
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000166:cytology; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D009865:Oocytes / Q000166:cytology*; D009994:Osmolar Concentration