title: Blastocyst development rate impacts outcome in cryopreserved blastocyst transfer cycles.
abstract: OBJECTIVE
  To assess cycle outcome among day 5 and day 6 cryopreserved frozen-thawed blastocyst embryo transfers (FBET).
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Military-based assisted reproduction technology (ART) center.
  
  
  METHODS
  One hundred seventy-two nondonor, programmed cryopreserved embryo cycles.
  
  
  METHODS
  Fully expanded blastocysts on day 5 were cryopreserved on day 5, and those achieving this state on day 6 were cryopreserved on day 6. Leuprolide acetate was given for ovulation inhibition, and endometrial supplementation was by oral and vaginal estradiol. Progesterone in oil was administered, and blastocyst transfer occurred in the morning of the sixth day of progesterone.
  
  
  METHODS
  Implantation, pregnancy, and live-birth rates.
  
  
  RESULTS
  Fresh and frozen cycle characteristics were similar between groups. Day-5 FBET had statistically significantly higher implantation rates (32.2% vs. 19.2%), which remained significant even when adjusting for covariates (odds ratio: 1.91; 95% confidence interval, 1.00, 3.67). Live-birth rates trended toward improvement after adjusting for covariates (odds ratio: 1.18; 95% confidence interval, 0.61, 2.30).
  
  
  CONCLUSIONS
  Cryopreserved day-5 blastocysts have higher implantation rates and trend toward improved pregnancy outcomes compared with cryopreserved day-6 blastocysts. This suggests that embryo development rate may, in part, predict implantation and subsequent FBET outcomes, although embryos not achieving the blastocyst stage until day 6 still demonstrate acceptable outcomes.
authors.affiliation: Walter Reed Army Medical Center ART Program, Washington, DC, USA. levense@mail.nih.gov
authors.forename: Eric D
authors.initials: ED
authors.lastname: Levens
authors.forename: Brian W
authors.initials: BW
authors.lastname: Whitcomb
authors.forename: Sasha
authors.initials: S
authors.lastname: Hennessy
authors.forename: Aidita N
authors.initials: AN
authors.lastname: James
authors.forename: Belinda J
authors.initials: BJ
authors.lastname: Yauger
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Larsen
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation; D046149:Embryo Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer; D047108:Embryonic Development; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007246:Infertility / Q000628:therapy*; D050498:Live Birth; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome