title: Oocyte vitrification as an efficient option for elective fertility preservation.
abstract: OBJECTIVE
  To provide a detailed description of the current oocyte vitrification status as a means of elective fertility preservation (EFP).
  
  
  METHODS
  Retrospective observational multicenter study.
  
  
  METHODS
  Private university-affiliated center.
  
  
  METHODS
  A total of 1,468 women who underwent EFP because of age or having associated a medical condition other than cancer (January 2007 to April 2015).
  
  
  METHODS
  None.
  
  
  METHODS
  Survival and cumulative live birth rate (CLBR) per consumed oocyte.
  
  
  RESULTS
  Mean age was higher with EFP due to age versus having an associated medical reason (37.7 y [95% confidence interval (CI) 36.5-37.9] vs. 35.7 y [95% CI 34.9-36.3]). In total, 137 patients (9.3%) returned to use their oocytes. Overall survival rate was 85.2% (95% CI 83.2-87.2). Live birth rate per patient was higher in women ≤35 years old than ≥36 years old (50% [95% CI 32.7-67.3] vs. 22.9% [95% CI 14.9-30.9]). CLBR was higher and increased faster in younger women. The gain in CLBR was sharp from 5 (15.4%, 95% CI -4.2 to 35.0) to 8 oocytes (40.8%, 95% CI 13.2-68.4), with an 8.4% gain per additional oocyte, in the ≤35-year-old group. The increase was slower with 10-15 oocytes, reaching a plateau CLBR of 85.2%. A milder increase (4.9% gain) was observed in the ≥36-year-old group (from 5.1% [95% CI -0.6 to 10.7] to 19.9% [95% CI 8.7-31.1] when 5-8 oocytes were consumed), reaching the plateau with 11 oocytes (CLBR 35.6%). Forty babies were born.
  
  
  CONCLUSIONS
  At least 8-10 metaphase II oocytes are necessary to achieve reasonable success. Numbers should be individualized in women >36 years old. We suggest encouraging women who are motivated exclusively by a desire to postpone childbearing because of age, to come at younger ages to increase success possibilities.
authors.affiliation: IVI-Valencia, Institut Universitari IVI, Valencia, Spain. Electronic address: ana.cobo@ivi.es.
authors.forename: Ana
authors.initials: A
authors.lastname: Cobo
authors.affiliation: IVI-Madrid, Universidad Rey Juan Carlos, Madrid, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: García-Velasco
authors.affiliation: IVI-Valencia, Institut Universitari IVI, Valencia, Spain.
authors.forename: Aila
authors.initials: A
authors.lastname: Coello
authors.affiliation: IVI-Las Palmas, Las Palmas, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Domingo
authors.affiliation: IVI Foundation, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pellicer
authors.affiliation: IVI-Valencia, Institut Universitari IVI, Valencia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Remohí
mesh_terms: D000328:Adult; D000367:Age Factors; D015925:Cryopreservation; D004624:Embryo Transfer; D005260:Female; D005298:Fertility; D059247:Fertility Preservation / Q000009:adverse effects / Q000379:methods*; D005307:Fertilization in Vitro; D006801:Humans; D007247:Infertility, Female / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D050498:Live Birth; D008677:Metaphase; D054315:Oocyte Retrieval / Q000009:adverse effects / Q000379:methods*; D009865:Oocytes; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D012307:Risk Factors; D013030:Spain; D016896:Treatment Outcome; D058989:Vitrification
keywords: Fertility preservation; live birth; oocyte vitrification; survival rate