title: Blastocyst culture after repeated failure of cleavage-stage embryo transfers: a comparison of day 5 and day 6 transfers.
abstract: OBJECTIVE
  To evaluate the efficacy of blastocyst transfer among patients with at least three previous cleavage-stage embryo transfer failures and to compare pregnancy and implantation rates of blastocysts according to the day of embryo transfer (day 5 or day 6 after oocyte retrieval).
  
  
  METHODS
  Retrospective clinical study.
  
  
  METHODS
  Private ART center.
  
  
  METHODS
  One hundred forty-eight patients (with at least three failed cleavage-stage embryo transfers) undergoing blastocyst-stage embryo transfer.
  
  
  METHODS
  Embryos were grown for up to 6 days and only blastocyst-stage (cavitating) embryos were transferred on either day 5 or day 6 after oocyte retrieval.
  
  
  METHODS
  Clinical pregnancy and implantation rates.
  
  
  RESULTS
  Blastocysts transferred on day 5 implanted almost five times the rate of those transferred on day 6 (23% vs. 5%). Pregnancy rates were triple as high among the 73 day 5 patients compared to the 63 day 6 transfer patients (38% vs. 11%). The number of blastocysts formed and per embryo rates of blastocyst formation were both significantly higher for patients undergoing day 5 transfers: more blastocysts developed (3.0 vs. 2.1) and more were transferred (3.0 vs. 1.9). In addition, blastocyst formation rates were 46% and 33%, respectively, for both groups of patients.
  
  
  CONCLUSIONS
  Blastocyst transfer (preferably on day 5 after retrieval) appears to be a successful and improved alternative for patients with multiple failed IVF attempts. Moreover, with blastocyst transfer there should be a reduction in multiple pregnancy risk, because fewer embryos have to be transferred.
authors.affiliation: Center for Reproductive Medicine and Fertility, Quirón Bilbao, Bilbao, Spain. gorkabz@euskalnet.net
authors.forename: Gorka
authors.initials: G
authors.lastname: Barrenetxea
authors.forename: Arantza
authors.initials: A
authors.lastname: López de Larruzea
authors.forename: Teresa
authors.initials: T
authors.lastname: Ganzabal
authors.forename: Rosario
authors.initials: R
authors.lastname: Jiménez
authors.forename: Koldo
authors.initials: K
authors.lastname: Carbonero
authors.forename: Miren
authors.initials: M
authors.lastname: Mandiola
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D009924:Organ Culture Techniques; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies