title: Birth of two babies using oocytes that were cryopreserved in a choline-based freezing medium.
abstract: BACKGROUND
  Oocyte cryopreservation may have significant potential for assisted reproductive technology. However, to date, successful results have been limited. We report a preliminary series of IVF outcomes after fertilization of oocytes that were frozen in a low-sodium medium.
  
  
  METHODS
  In this retrospective analysis, 12 patients (21-41 years old), who underwent IVF in a fertility clinic affiliated to the University of Buenos Aires, had oocytes cryopreserved in a modified phosphate buffered saline medium, in which sodium chloride was replaced by choline chloride. A slow-freezing, rapid-thawing protocol was used and oocytes were inseminated by ICSI. Outcome measures included oocyte survival, fertilization, implantation and pregnancy rates.
  
  
  RESULTS
  Median oocyte survival was 63%. Median fertilization rate was 59%. Overall implantation rate was 25%. Six clinical pregnancies were achieved; two of these pregnancies went to term resulting in the birth of two babies.
  
  
  CONCLUSIONS
  To the best of our knowledge, these are the first pregnancies and normal births using oocytes that were cryopreserved in a choline-based medium. The small sample size prevents us from concluding that freezing in a low-sodium medium is superior to using a conventional one.
authors.affiliation: Halitus Instituto Médico, Affiliated to the University of Buenos Aires, Marcelo T de Alvear 2084 (C1122AAF), Buenos Aires, Argentina. cquintans@halitus.com
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Quintans
authors.forename: Mónica J
authors.initials: MJ
authors.lastname: Donaldson
authors.forename: M Victoria
authors.initials: MV
authors.lastname: Bertolino
authors.forename: R Sergio
authors.initials: RS
authors.lastname: Pasqualini
mesh_terms: D000328:Adult; D002794:Choline; D015925:Cryopreservation / Q000379:methods*; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D011256:Pregnancy Outcome; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic
chemical_list: D002794:Choline