title: The importance of the cleavage stage morphology evaluation for blastocyst transfer in patients with good prognosis.
abstract: OBJECTIVE
  To evaluate: (i) the influence of morphology at cleavage stage on blastocyst formation and implantation, and (ii) whether the transfer of low-quality embryos on day-three would be a better approach than the transfer at blastocyst stage.
  
  
  METHODS
  This study included 8,444 embryos obtained from 1,125 patients undergoing ICSI cycles between January/2011 and September/2013. The influence of the quality of the embryo on days-two and -three on blastocyst formation and implantation success was evaluated. Moreover, the implantation potential of low-quality embryos, at cleavage stage, transferred on day-three was compared with the implantation potential of low-quality embryos, at cleavage stage, transferred on day-five.
  
  
  RESULTS
  Low-quality embryos on day-two had an approximate 20 % decreased chance of achieving the blastocyst stage, and blastocysts derived from low-quality embryos on day-two had a nearly 40 % decrease in the implantation chance. Low-quality embryos on day-three had a 30 % decreased chance of achieving the blastocyst stage, and blastocysts derived from low-quality embryos on day-three had an almost 40 % decreased implantation chance. The implantation rate didn't differ when low-quality embryos on the cleavage stage were transferred on day-three or left in culture and transferred on day-five.
  
  
  CONCLUSIONS
  The transfer of low-quality embryos on day-three is a better approach than transfer at the blastocyst stage. In addition, the embryo morphology evaluation at the cleavage stage is still needed for the selection of the embryo with the best implantation potential in extended embryo culture programmes.
authors.affiliation: Fertility - Assisted Fertilisation Centre, Av. Brigadeiro Luis Antônio 4545, São Paulo, SP, 01401-002, Brazil, dbraga@fertility.com.br.
authors.forename: Daniela P A F
authors.initials: DP
authors.lastname: Braga
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Setti
authors.forename: Rita C S
authors.initials: RC
authors.lastname: Figueira
authors.forename: Assumpto
authors.initials: A
authors.lastname: Iaconelli
authors.forename: Edson
authors.initials: E
authors.lastname: Borges
mesh_terms: D001755:Blastocyst; D002970:Cleavage Stage, Ovum / Q000637:transplantation*; D010064:Embryo Implantation / Q000502:physiology*; D004624:Embryo Transfer; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011379:Prognosis