title: Optimizing human oocyte cryopreservation for fertility preservation patients: should we mature then freeze or freeze then mature?
abstract: OBJECTIVE
  To evaluate the maturation and post-thaw survival rates of immature oocytes to determine whether in vitro maturation (IVM) should be attempted prior to or after cryopreservation.
  
  
  METHODS
  Nonrandomized observational study.
  
  
  METHODS
  Private academic and clinical reproductive center.
  
  
  METHODS
  Patients (n = 71) who donated immature unusable oocytes after vaginal oocyte retrieval (VOR) after undergoing controlled ovarian hyperstimulation using a standard GnRH antagonist protocol.
  
  
  METHODS
  Germinal vesicle (GV), metaphase I (MI), and metaphase II (MII) oocytes (n = 175) were obtained from consenting IVF patients for fresh IVM, post-thaw IVM, or control group. In the fresh IVM group, GV- and MI- stage oocytes (n = 69) were cultured for 24 hours, matured in vitro (IVM-MII), cryopreserved, thawed, and evaluated for survival. In the post-thaw IVM group, GV- and MI- stage oocytes (n = 27) were frozen on day 0, thawed, evaluated for survival, and cultured for 24-hour IVM. MII donor oocytes (n = 79) were cryopreserved and thawed as a control.
  
  
  METHODS
  Survival postfreeze and oocyte development to the MII stage was analyzed using a χ(2) analysis.
  
  
  RESULTS
  Fresh IVM had a significantly higher maturation rate than post-thaw IVM.
  
  
  CONCLUSIONS
  Oocyte cryopreservation is important for patients at risk of ovarian cancer, elective fertility preservation, and, potentially, for ovum donation. The superior maturation rate of GV and MI oocytes in the fresh versus post-thaw groups provides strong evidence for maturing oocytes to the MII stage before cryopreservation.
authors.affiliation: Reproductive Medicine Associates of New York, New York, NY 10022, USA. jlee@rmany.com
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Lee
authors.forename: Jason
authors.initials: J
authors.lastname: Barritt
authors.forename: Rose Marie
authors.initials: RM
authors.lastname: Moschini
authors.forename: Richard E
authors.initials: RE
authors.lastname: Slifkin
authors.forename: Alan B
authors.initials: AB
authors.lastname: Copperman
mesh_terms: D002470:Cell Survival; D015925:Cryopreservation / Q000379:methods* / Q000592:standards; D005260:Female; D005298:Fertility; D059247:Fertility Preservation / Q000379:methods* / Q000592:standards; D006801:Humans; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods* / Q000592:standards; D008677:Metaphase; D018587:Oocyte Donation; D054315:Oocyte Retrieval; D009865:Oocytes / Q000166:cytology*; D010051:Ovarian Neoplasms; D027724:Reproductive Techniques, Assisted / Q000592:standards