title: Incidence and development of zygotes exhibiting abnormal pronuclear disposition after identification of two pronuclei at the fertilization check.
abstract: OBJECTIVE
  To determine the incidence, developmental potential, and clinical implications of embryos having one pronucleus (1PN) or three pronuclei (3PN) at early cleavage, despite exhibiting 2PN at the fertilization check.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Hospital-based academic medical center.
  
  
  METHODS
  All IVF cycles from January 2006 through May 2008 having 2PN zygotes that subsequently transitioned to 1PN or 3PN before cleavage, matched to cycles having 2PN zygotes progressing to cleavage without intervening abnormal pronuclear disposition.
  
  
  METHODS
  Standard IVF protocol.
  
  
  METHODS
  Incidence, day 3 development, and implantation rates of 2PN zygotes transitioning to 1PN and 3PN states before cleavage, compared with normal embryos.
  
  
  RESULTS
  The incidences of 1PN and 3PN zygotes were 2.9% and 0.4%, respectively. Both types of abnormal zygote showed slower day 3 cleavage, although only the 1PNs exhibited higher fragmentation and asymmetry compared with controls. The 1PN zygotes had a 6.4% implantation rate and viable pregnancy rate of 1.3%. Of the nine 3PN zygotes transferred, none implanted.
  
  
  CONCLUSIONS
  Two-pronuclear zygotes transitioning through 1PN or 3PN states tend to develop into poorer-quality embryos than 2PN control zygotes. Patients should be counseled regarding the very low likelihood of viable pregnancy after transfer of these abnormally developing zygotes.
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Reichman
authors.forename: Katharine V
authors.initials: KV
authors.lastname: Jackson
authors.forename: Catherine
authors.initials: C
authors.lastname: Racowsky
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002467:Cell Nucleus / Q000235:genetics / Q000473:pathology*; D002869:Chromosome Aberrations / Q000196:embryology* / Q000706:statistics & numerical data*; D002970:Cleavage Stage, Ovum; D015331:Cohort Studies; D010064:Embryo Implantation / Q000502:physiology; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005306:Fertilization / Q000502:physiology; D005307:Fertilization in Vitro; D006801:Humans; D015994:Incidence; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D019836:Preimplantation Diagnosis / Q000379:methods; D012189:Retrospective Studies; D015053:Zygote / Q000378:metabolism / Q000502:physiology