title: Factors associated with birth outcomes from cryopreserved blastocysts: experience from 4,597 autologous transfers of 7,597 cryopreserved blastocysts.
abstract: OBJECTIVE
  To evaluate factors associated with cryopreserved blastocyst transfer birth outcomes, including age, expansion time, cryopreservation protocol, cryodamage, and number of embryos transferred.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Private infertility practice.
  
  
  METHODS
  Cryopreserved blastocyst transfer patients from January 2003 to April 2012.
  
  
  METHODS
  None.
  
  
  METHODS
  Birth per transfer and children per embryo.
  
  
  RESULTS
  Overall live birth per transfer was 32%, with 17% twin births and 0.3% triplets. Live birth per transfer was significantly higher for vitrification compared with slow-freeze (day 5 cryopreservation: 47% vs. 35%; day 6 cryopreservation: 46% vs. 24%), as was live born children per transferred embryo (39% vs. 29% for day 5; 36% vs. 18% for day 6). Birth rates declined only slightly with increasing age at cryopreservation through 37 years, followed by an increasingly rapid decline in success with increasing age thereafter. Live birth rates declined rapidly (49%-18% for vitrification and 37%-10% for slow-freeze) as the percentage of intact cells after cryopreservation decreased from 95%-100% to 70%-79%, with almost no births when the percentage of intact cells was <70%. Increasing numbers of embryos per transfer were associated with significant increase in live birth per transfer but significant decrease in children per transferred embryo. Birth rates were much lower for blastocysts with delayed expansion on day 7 (10% per transfer).
  
  
  CONCLUSIONS
  Birth outcomes from cryopreserved blastocyst transfer are influenced by age, timing of expansion, cryopreservation protocol, visible cryodamage, and the number of embryos transferred. Vitrification substantially improves outcomes versus slow freezing.
authors.affiliation: Shady Grove Fertility Reproductive Science Center, Rockville, Maryland. Electronic address: kevin.richter@integramed.com.
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Richter
authors.affiliation: The George Washington University School of Medicine and Health Sciences, Washington, D.C.
authors.forename: Daniella K
authors.initials: DK
authors.lastname: Ginsburg
authors.affiliation: Shady Grove Fertility Reproductive Science Center, Rockville, Maryland.
authors.forename: Sharon K
authors.initials: SK
authors.lastname: Shipley
authors.affiliation: Shady Grove Fertility Reproductive Science Center, Rockville, Maryland.
authors.forename: Josh
authors.initials: J
authors.lastname: Lim
authors.affiliation: Shady Grove Fertility Reproductive Science Center, Rockville, Maryland.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tucker
authors.affiliation: Shady Grove Fertility Reproductive Science Center, Rockville, Maryland.
authors.forename: James R
authors.initials: JR
authors.lastname: Graham
authors.affiliation: Shady Grove Fertility Reproductive Science Center, Rockville, Maryland.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Levy
mesh_terms: D001757:Blastomeres / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000009:adverse effects / Q000379:methods; D005260:Female; D005298:Fertility; D005307:Fertilization in Vitro; D006801:Humans; D007246:Infertility / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D011247:Pregnancy; D018873:Pregnancy Rate; D059286:Pregnancy, Triplet; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D012307:Risk Factors; D056826:Single Embryo Transfer; D013997:Time Factors; D016896:Treatment Outcome
keywords: Cryopreservation; blastocyst; live birth; slow-freeze; vitrification