title: Influence of post-thaw culture on the developmental potential of human frozen embryos.
abstract: OBJECTIVE
  Apart from freezing/thawing related cryodamage, several additional factors have been identified as major players in the reduction of success rates after frozen embryo transfers. The post-thaw culture is particularly relevant as it may amplify environmental influences over a stressed embryo. In the present study the influence of the post-thaw culture duration on the implantation and developmental potential of cleavage stage embryos was evaluated.
  
  
  METHODS
  In this retrospective evaluation, that spanned an 8-year period, 631 frozen-thawed embryos were allocated to one of two study groups, depending on their post-thaw culture period: 1) the long (18-24 h), or 2) the short (2-5 h) culture group. Groups were compared regarding implantation rate and live birth rate per embryo transferred. This comparison was corrected for the most common confounding factors such as maternal age at oocyte pick-up, number of transferred embryos, developmental day at freezing, blastomere survival after thawing, catheter used for transfer and year of procedure.
  
  
  RESULTS
  Implantation and live birth rate per embryo transferred were inversely related to the duration of the post-thaw culture, as diminishing this period significantly increased both rates. Moreover, no advantage could be found for a long post-thaw culture period, even for embryos with observed mitotic activity.
  
  
  CONCLUSIONS
  This retrospective analysis indicates that a short post-thaw culture period is associated with higher implantation and live birth rates per embryo. This study supports selection of frozen-thawed embryos strictly based on blastomere cryosurvival and raises the hypothesis that environmental factors may have an important role on embryo implantation and developmental potential during post-thaw culture.
authors.affiliation: Centro Médico de Assistência à Reprodução-CEMEARE, Rua Alfredo Mesquita, 2E, 1600-922, Lisbon, Portugal.
authors.forename: Mafalda L
authors.initials: ML
authors.lastname: Rato
authors.forename: António
authors.initials: A
authors.lastname: Gouveia-Oliveira
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Plancha
mesh_terms: D000328:Adult; D001757:Blastomeres / Q000166:cytology / Q000378:metabolism; D002970:Cleavage Stage, Ovum / Q000378:metabolism / Q000502:physiology; D015925:Cryopreservation; D003470:Culture Media / Q000378:metabolism*; D046149:Embryo Culture Techniques / Q000379:methods*; D004624:Embryo Transfer / Q000379:methods; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D050498:Live Birth; D008423:Maternal Age; D008938:Mitosis; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D003470:Culture Media