title: Oocyte cryopreservation outcomes including pre-cryopreservation and post-thaw meiotic spindle evaluation following slow cooling and vitrification of human oocytes.
abstract: OBJECTIVE
  To report our oocyte cryopreservation (OC) outcomes including meiotic spindle (MS) evaluation of metaphase II (MII) oocytes destined for OC and thaw.
  
  
  METHODS
  Retrospective.
  
  
  METHODS
  University-based infertility center.
  
  
  METHODS
  Women attempting pregnancy using cryopreserved oocytes.
  
  
  METHODS
  OC, MS evaluation.
  
  
  METHODS
  Survival, two pronuclear (2PN) fertilization, achieving embryo quality suitable for transfer or refreezing, blastocyst formation.
  
  
  RESULTS
  Thirty-two OC-thaw cycles resulted in 20 pregnancies, 18 either ongoing or delivered. In 26 cycles, MS evaluation was performed: 262/303 (86%) thawed/recovered oocytes survived, 218/262 (83%) achieved 2PN fertilization, 133/218 (61%) became suitable for day-3 and 122/218 (56%) for day-5 transfer. In total, 58 embryos were transferred resulting in a 62% pregnancy and a 41% implantation rate. Of oocytes evaluated before cryopreservation, 247 (82%) were spindle-positive; 96% of these were also spindle-positive after thawing. Blastocyst formation and suitability for day-5 transfer was achieved more often if a post-thaw spindle was visualized. Of all slow-cooled and vitrified oocytes, a higher percentage of those slow-cooled achieved 2PN fertilization and usability. MS evaluation of oocytes cryopreserved by either method was associated with similar outcomes.
  
  
  CONCLUSIONS
  OC outcomes are improving. An MS was almost always exhibited both before cryopreservation and after thawing, suggesting that, with appropriate technique, OC presents minimal harm to the MII oocyte. A meiotic spindle evaluation might help to further OC technology.
authors.affiliation: New York University Fertility Center, New York University School of Medicine, New York, New York 10021, USA. nnoyes01@gmail.com
authors.forename: Nicole
authors.initials: N
authors.lastname: Noyes
authors.forename: Jaime
authors.initials: J
authors.lastname: Knopman
authors.forename: Patty
authors.initials: P
authors.lastname: Labella
authors.forename: Caroline
authors.initials: C
authors.lastname: McCaffrey
authors.forename: Melicia
authors.initials: M
authors.lastname: Clark-Williams
authors.forename: Jamie
authors.initials: J
authors.lastname: Grifo
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D008540:Meiosis / Q000502:physiology; D009865:Oocytes; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D008941:Spindle Apparatus / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D016896:Treatment Outcome