title: Multicenter observational study on slow-cooling oocyte cryopreservation: clinical outcome.
abstract: OBJECTIVE
  To evaluate the efficacy of oocyte cryopreservation by a single slow-cooling protocol involving sucrose (0.2 mol/L) in the freezing solution.
  
  
  METHODS
  Observational comparison of the clinical outcome in fresh and frozen thawed cycles.
  
  
  METHODS
  Public and private IVF centers.
  
  
  METHODS
  Infertile couples undergoing IVF treatment.
  
  
  METHODS
  Use of a maximum three oocytes in fresh cycles, as established by local law, and cryopreservation and later use of surplus oocytes. Likewise fresh cycles, maximum three thawed oocytes were used per cycle. All thawed oocytes were microinjected.
  
  
  METHODS
  Embryologic and clinical parameters of fresh and thawed cycles.
  
  
  RESULTS
  Two thousand forty-six patients underwent 2,209 oocyte retrievals involving oocyte cryopreservation. Overall, the survival rate of thawed oocytes was 55.8%. In 940 thaw cycles, the mean numbers of inseminated oocytes and fertilization rates were significantly decreased vs. fresh cycles outcomes (2.6 ± 0.7 vs. 2.9 ± 0.2 and 72.5% vs. 78.3%, respectively), as were the rates of implantation (10.1% vs. 15.4%), pregnancy rates per transfer (17.0% vs. 27.9%), and pregnancy rates per cycle (13.7% vs. 26.2%). Differences in clinical outcome were found among centers. A pregnancy rate per thawing cycle above 14% was achieved by most clinics. Fifty-seven retrievals involving oocyte cryopreservation achieved a pregnancy after fresh embryo replacement. Implantation and pregnancy rates per embryo transfer and per thawing cycles were 17.5%, 28.6%, and 24.6%, respectively.
  
  
  CONCLUSIONS
  Under the conditions tested, the clinical outcome of oocyte slow-cooling cryopreservation is reduced compared with fresh cycles. Nevertheless, in cases of inapplicability of embryo cryopreservation, oocyte cryopreservation should be offered to patients with surplus oocytes.
authors.affiliation: Tecnobios Procreazione, Centre for Reproductive Health, Bologna, Italy. borini@tecnobiosprocreazione.it
authors.forename: Andrea
authors.initials: A
authors.lastname: Borini
authors.forename: Paolo Emanuele
authors.initials: PE
authors.lastname: Levi Setti
authors.forename: Paola
authors.initials: P
authors.lastname: Anserini
authors.forename: Roberto
authors.initials: R
authors.lastname: De Luca
authors.forename: Lucia
authors.initials: L
authors.lastname: De Santis
authors.forename: Eleonora
authors.initials: E
authors.lastname: Porcu
authors.forename: Giovanni Battista
authors.initials: GB
authors.lastname: La Sala
authors.forename: Annapia
authors.initials: A
authors.lastname: Ferraretti
authors.forename: Tiziana
authors.initials: T
authors.lastname: Bartolotti
authors.forename: Giovanni
authors.initials: G
authors.lastname: Coticchio
authors.forename: Giulia
authors.initials: G
authors.lastname: Scaravelli
mesh_terms: D000328:Adult; D001723:Birth Rate; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D003451:Cryoprotective Agents; D013395:Sucrose