title: Twice-frozen embryos are no detriment to pregnancy success: a retrospective comparative study.
abstract: OBJECTIVE
  To compare the pregnancy rates (PR) and live birth rates in once- versus twice-frozen ET treatment cycles in the same cohort of women.
  
  
  METHODS
  A retrospective study.
  
  
  METHODS
  Fertility clinics, IVF Australia, New South Wales.
  
  
  METHODS
  The study population was all women who underwent thawing of twice-frozen embryos between January 2003 and May 2009.
  
  
  METHODS
  Twice-frozen, twice-thawed embryos.
  
  
  METHODS
  Pregnancy and live birth rate.
  
  
  RESULTS
  There were 44 women who had 52 twice-frozen ET treatment cycles. The mean age of the women was 32 ± 4.4 years and the mean number of embryos transferred was 1.1 in both the once-frozen and twice-frozen ET treatment cycles. Twice-frozen embryos had a lower post-thaw survival rate compared with the once-frozen embryos. There was no significant difference in the clinical PR or live birth rate per ET between twice-frozen and once-frozen ETs.
  
  
  CONCLUSIONS
  Twice-frozen-thawed embryos have a lower post- thaw survival rate but equivalent pregnancy and live birth rates to once-frozen embryos. Further studies are necessary to confirm our findings and to assess long-term safety outcomes.
authors.affiliation: IVF Australia, New South Wales, Australia. drjuliettekoch@gmail.com
authors.forename: Juliette
authors.initials: J
authors.lastname: Koch
authors.forename: Michael F
authors.initials: MF
authors.lastname: Costello
authors.forename: Michael G
authors.initials: MG
authors.lastname: Chapman
authors.forename: Suha
authors.initials: S
authors.lastname: Kilani
mesh_terms: D000328:Adult; D001723:Birth Rate / Q000639:trends*; D015331:Cohort Studies; D015925:Cryopreservation / Q000379:methods*; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate / Q000639:trends; D012189:Retrospective Studies; D016896:Treatment Outcome