title: Time from insemination to first cleavage predicts developmental competence of human preimplantation embryos in vitro.
abstract: BACKGROUND
  The absence of reliable markers for the identification of viable embryos for transfer at the early cleavage stage is likely to contribute to the generally low implantation rates and high incidence of multiple gestation in IVF treatment. In this study, we investigate the relationship between timing of first cleavage and the incidence of blastocyst formation in vitro.
  
  
  METHODS
  Couples (n = 70) with at least one embryo remaining after transfer were included in the analyses. All embryos (n = 579) were examined for early cleavage at 25 h after insemination. Following embryo transfer, the remaining embryos (n = 426) were cultured until day 7 of development, and assessed for blastocyst formation.
  
  
  RESULTS
  Eighty-five embryos (14.7%) cleaved to the 2-cell stage within 25 h of insemination; 26 of these were selected for transfer on day 2. Of the 59 embryos remaining in culture, 19 (32.2%) developed to the blastocyst stage; this was a significantly higher number than was observed in embryos (61/367; 16.6%) that failed to cleave within 25 h of insemination (P < 0.01). Within these two groups of embryos the proportion of hatched blastocysts was 11/59 (18.6%) and 26/367 (7.1%) respectively (P < 0.005).
  
  
  CONCLUSIONS
  These findings indicate that early cleavage is indicative of increased developmental potential in human embryos and may be useful as an additional criterion in the selection of embryos for transfer.
authors.affiliation: Reproductive Medicine, BioScience Centre, ICFL, Times Square, Newcastle upon Tyne NE1 4EP, UK.
authors.forename: J
authors.initials: J
authors.lastname: Fenwick
authors.forename: P
authors.initials: P
authors.lastname: Platteau
authors.forename: A P
authors.initials: AP
authors.lastname: Murdoch
authors.forename: M
authors.initials: M
authors.lastname: Herbert
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000166:cytology / Q000502:physiology*; D002452:Cell Count; D002970:Cleavage Stage, Ovum; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro; D005544:Forecasting; D006801:Humans; D013997:Time Factors