title: Cryopreservation of human embryos at the morula stage and outcomes after transfer.
abstract: OBJECTIVE
  To evaluate the survival rate of human morula embryo freezing and the morphological alterations during freezing, during and after thawing, and their applications in embryo selection.
  
  
  METHODS
  Retrospective observational study.
  
  
  METHODS
  Private infertility clinic.
  
  
  METHODS
  Consecutive patients under age 39 undergoing frozen morula embryo transfers from December 1999 to May 2003.
  
  
  METHODS
  Embryo freezing was performed at the morula stage. Embryo thaw and post-thaw ETs were conducted on the same day, which is equivalent to a day 4 ET.
  
  
  METHODS
  Morphological alterations during freezing and thawing and after thawing. Post-thaw embryo survival rates, transferable rates, pregnancy rates, and implantation rates.
  
  
  RESULTS
  Morula embryos showed reversed morphological alterations during the freezing process; these alterations were recovered during thawing or shortly after the thawing. Post-thaw survival rates showed no significant difference between any of the morula substages. However, embryos scored as grade 3, which represented good quality, had significantly higher post-thaw survival and transferable rates than grade 2 and 1 embryos. Patients who received at least one grade 3 embryo had significantly higher pregnancy rates, implantation rates, and ongoing/live birth rates than other groups.
  
  
  CONCLUSIONS
  An acceptable survival rate can be achieved after cryopreservation of human morula embryos, and morphological alterations that occur during and shortly after an embryo thaw can be a feasible index for determining viable embryos.
authors.affiliation: Fertility Treatment Center, Chandler, Arizona, USA. jtao@fertilitytreatmentcenter.com
authors.forename: Jun
authors.initials: J
authors.lastname: Tao
authors.forename: Randall H
authors.initials: RH
authors.lastname: Craig
authors.forename: Mark
authors.initials: M
authors.lastname: Johnson
authors.forename: Brenda
authors.initials: B
authors.lastname: Williams
authors.forename: Wendy
authors.initials: W
authors.lastname: Lewis
authors.forename: Jennifer
authors.initials: J
authors.lastname: White
authors.forename: Nicole
authors.initials: N
authors.lastname: Buehler
mesh_terms: D015925:Cryopreservation; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D009028:Morula / Q000166:cytology / Q000502:physiology; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D014022:Tissue Survival; D016896:Treatment Outcome