title: Frozen-thawed embryo transfer cycles.
abstract: OBJECTIVE
  To review the outcomes of frozen-thawed embryo transfer cycles. DESIGN. Retrospective review.
  
  
  METHODS
  Tertiary assisted reproduction centre, Hong Kong.
  
  
  METHODS
  Subfertile patients undergoing frozen-thawed embryo transfer between July 2005 and December 2007.
  
  
  METHODS
  Clinical and ongoing pregnancy rates.
  
  
  RESULTS
  A total of 983 frozen-thawed embryo transfer cycles performed during the study period were reviewed. The clinical pregnancy and ongoing pregnancy rates were 35% and 30%, respectively. Factors associated with successful outcome included younger maternal age (<=35 years) and 4 or more blastomeres at replacement, but not the method of insemination, the cause of subfertility, or the type of frozen-thawed embryo transfer cycle. The overall multiple pregnancy rate was 18%. For cycles with a single embryo replaced, embryos having 4-cell or higher stages at replacement gave an ongoing pregnancy rate of 25%, whereas those with less than 4 cells had a significantly lower ongoing pregnancy rate of 5% only. Blastomere lysis after thawing significantly reduced the clinical pregnancy and ongoing pregnancy rates of cycles with one embryo replaced.
  
  
  CONCLUSIONS
  Clinical pregnancy and ongoing pregnancy rates of frozen-thawed embryo transfer cycles were 35% and 30%, respectively. Higher pregnancy rates were associated with younger maternal age (<=35 years), blastomere numbers of 4 or more, and no blastomere lysis after thawing.
authors: Department of Obstetrics and Gynaecology, Centre of Assisted Reproduction and Embryology, The University of Hong Kong, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong.
authors: William S B
authors: WS
authors: Yeung
authors: Raymond H W
authors: RH
authors: Li
authors: T M
authors: TM
authors: Cheung
authors: Ernest H Y
authors: EH
authors: Ng
authors: Estella Y L
authors: EY
authors: Lau
authors: P C
authors: PC
authors: Ho
mesh_terms: D000328:Adult; D001757:Blastomeres / Q000637:transplantation; D015925:Cryopreservation; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple; D012189:Retrospective Studies