title: Transfer of blastocysts derived from frozen-thawed cleavage stage embryos improved ongoing pregnancy.
abstract: OBJECTIVE
  The aim of our study was to compare the transfer of embryos that are cryopreserved in cleavage stage after thawing with the transfer of embryos after thawing and culture in sequential media until blastocyst formation.
  
  
  METHODS
  In this prospective clinical study, we have evaluated 134 cycles of ART treatment for infertility. Frozen embryos were thawed and then cultured in sequential media until blastocyst stage in blastocyst group and were compared with thawed embryos in cleavage stage group.
  
  
  RESULTS
  Implantation rate was significantly higher in blastocyst group (30 %) compared to cleavage group (17 %). No statistical differences were reported in chemical and clinical pregnancy rates between groups. Ongoing pregnancy rate was significantly higher in blastocyst group compared to cleavage group (42.9 vs. 24.6 %).
  
  
  CONCLUSIONS
  Our results indicated that blastocyst formation after thawing of cleavage stage embryos is a good predictor for embryo viability and pregnancy outcome.
authors.affiliation: Department of Obstetrics and Gynecology, Research and Clinical Center for Infertility, Shahid Sadoughi University of Medical Sciences, Bouali Ave, Safaeiyeh, Yazd, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Eftekhar
authors.forename: Abbas
authors.initials: A
authors.lastname: Aflatoonian
authors.forename: Farnaz
authors.initials: F
authors.lastname: Mohammadian
authors.forename: Nasim
authors.initials: N
authors.lastname: Tabibnejad
mesh_terms: D000328:Adult; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D046509:Tissue Culture Techniques; D055815:Young Adult