title: Early cleavage of human embryos: an effective method for predicting successful IVF/ICSI outcome.
abstract: BACKGROUND
  The need for effective parameters for selecting the best embryos is paramount when a large number of them are available for transfer. Other studies have reported that transfer of pre-selected embryos, based on cleavage to the 2-cell stage at 25 h and 27 h post-insemination/intracytoplasmic sperm injection (ICSI), increases implantation and pregnancy rates. We investigated whether extending the time for selection of cleaved embryos to 29 h post-insemination/ICSI had a similar effect on pregnancy and implantation rates.
  
  
  METHODS
  Cleavage to the 2-cell stage was assessed at 25, 27 and 29 h post-insemination/ICSI. Embryos that had cleaved at any of these time points were designated as 'early cleavage' (EC), while others were designated as 'non-early cleavage' (NEC). EC embryos were selected and preferentially transferred.
  
  
  RESULTS
  EC occurred in 57% of the cycles (61% IVF; 51% ICSI). Significantly (P = 0.02) more clinical pregnancies occurred in the EC group (23/42, 55%) compared with the group that had no embryo undergoing first cleavage up to 29 h post-insemination/ICSI (8/32, 25%). The EC group of patients was significantly younger than the NEC.
  
  
  CONCLUSIONS
  Transfer of selected embryos that reached the 2-cell stage between 25 and 29 h post-insemination/ICSI is a reliable prognostic tool for patients undergoing assisted reproduction techniques.
authors.affiliation: Fundação Universitária de Endocrinologia e Fertilidade, Rua Alcides Cruz 101, CEP: 90.630-160, Porto Alegre, RS, Brazil. adriana@orion.ufrgs.br
authors.forename: A
authors.initials: A
authors.lastname: Bos-Mikich
authors.forename: A L
authors.initials: AL
authors.lastname: Mattos
authors.forename: A N
authors.initials: AN
authors.lastname: Ferrari
mesh_terms: D000328:Adult; D002970:Cleavage Stage, Ovum; D010064:Embryo Implantation; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D011247:Pregnancy; D020554:Sperm Injections, Intracytoplasmic; D013997:Time Factors; D016896:Treatment Outcome