title: Oocyte slow freezing using a 0.2-0.3 M sucrose concentration protocol: is it really the time to trash the cryopreservation machine?
abstract: OBJECTIVE
  To update results on outcomes with frozen/thawed oocytes using a differential sucrose concentration during dehydration (0.2 M) and rehydration (0.3 M), combined with a one-step propanediol exposure.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Private IVF centers.
  
  
  METHODS
  Infertile couples undergoing IVF treatment.
  
  
  METHODS
  Oocyte thawing cycles between May 2004 and December 2010.
  
  
  METHODS
  Survival, fertilization, and cleavage rates were reported to evaluate biological outcomes. Clinical pregnancy and implantation rates were analyzed as markers of efficiency.
  
  
  RESULTS
  Three hundred forty-two patients and 443 cycles were monitored; the survival was 71.8%, fertilization 77.9%, and of the embryos obtained 83.8% were classified as grade 1 and 2. Three hundred ninety-four transfers were performed, resulting in 90 pregnancies. The pregnancy rate per transfer was 22.8% and per patient was 26.3%, with 122 gestational sacs. The implantation rate per embryo was 13.5%. Patients were divided into three groups according to their age: ≤ 34 years (group A), 35-38 years (group B), and ≥ 39 years (group C). Biological outcomes were comparable in all three groups, whereas the pregnancy rate per transfer was higher in the first group (27.7% vs. 21.4% and 17.6%). The implantation rates per injected egg were 11.8%, 8.0%, and 7.5% for the three groups, respectively.
  
  
  CONCLUSIONS
  The biological and clinical data obtained on 443 cycles are consistent with our previous results showing that slow freezing of oocytes can be a valid tool in IVF practice when performed with a suitable protocol.
authors.affiliation: Tecnobios Procreazione, Centre for Reproductive Health, Bologna, Italy.
authors.forename: Veronica
authors.initials: V
authors.lastname: Bianchi
authors.forename: Michela
authors.initials: M
authors.lastname: Lappi
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Bonu
authors.forename: Andrea
authors.initials: A
authors.lastname: Borini
mesh_terms: D000328:Adult; D002470:Cell Survival / Q000187:drug effects; D016009:Chi-Square Distribution; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology*; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007246:Infertility / Q000503:physiopathology / Q000628:therapy*; D007558:Italy; D054315:Oocyte Retrieval; D009865:Oocytes / Q000187:drug effects* / Q000473:pathology; D011247:Pregnancy; D018873:Pregnancy Rate; D011409:Propylene Glycols / Q000494:pharmacology; D012189:Retrospective Studies; D013395:Sucrose / Q000494:pharmacology*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D003451:Cryoprotective Agents; D011409:Propylene Glycols; D013395:Sucrose