title: Phasing-in of vitrification into routine practice: why, how, and what.
abstract: OBJECTIVE
  To evaluate and compare the laboratory and clinical outcomes of vitrification with slow-freezing method for cryopreservation of embryos and blastocysts in an in-vitro fertilisation programme.
  
  
  METHODS
  Retrospective analysis of all the 104 cycles of frozen embryo and blastocyst replacements from 2003 to 2008 and all the 149 cycles with embryos or blastocysts for vitrification from 2006 to 2009.
  
  
  METHODS
  Hospital-based Licensed Assisted Reproduction Treatment Centre in Hong Kong.
  
  
  METHODS
  All participants having frozen embryos or blastocysts transfer from 2003 to 2008.
  
  
  METHODS
  Surplus embryos and blastocysts after fresh transfer were cryopreserved by vitrification method.
  
  
  METHODS
  Cryosurvival rate after freeze-thawing of early cleavage embryos and blastocysts by the two cryopreservation methods of slow-freezing and vitrification, and the pregnancy rate, implantation rate, delivery rate and live-birth rate achieved.
  
  
  RESULTS
  Cryosurvival rates of both vitrified blastocysts (79%) and early cleavage-stage embryos (88%) were significantly higher, as compared with the slow-freezing groups (57% and 72% respectively, both P<0.05). Pregnancy rates, delivery rates, and implantation rates were all significantly higher with vitrification regardless of the embryo types. Both implantation and live-birth rates were higher (31%, odds ratio=14 and 27%, odds ratio=11, respectively) per vitrified blastocyst transferred as compared with slow-freezing (both 3%).
  
  
  CONCLUSIONS
  Vitrification improved clinical outcomes of both frozen embryos and especially blastocyst transfers. It conferred upon both blastocysts and embryos better developmental potential after the vitrify-thaw procedure.
authors.affiliation: Dr Stephen Chow Chun-kay Assisted Reproduction Centre, Department of Obstetrics and Gynaecology, Kwong Wah Hospital, Kowloon, Hong Kong. jwongyy200505@netvigator.com
authors.forename: Jacki Y Y
authors.initials: JY
authors.lastname: Wong
authors.forename: Alice Y K
authors.initials: AY
authors.lastname: Wong
mesh_terms: D015925:Cryopreservation / Q000379:methods*; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D011247:Pregnancy; D012189:Retrospective Studies; D058989:Vitrification