title: In-vitro maturation of human oocytes: before or after vitrification?
abstract: OBJECTIVE
  This study aims to determine if in-vitro maturation (IVM) of human immature oocytes should be performed before or after vitrification.
  
  
  METHODS
  A total of 184 immature oocytes were randomly divided into two different groups: 100 were vitrified at metaphase II (MII) stage 24 h-48 h after IVM (group 1) and 84 were immediately vitrified at germinal vesicle (GV) or metaphase I (MI) stages and in vitro matured after warming (group 2).
  
  
  RESULTS
  Survival rate after warming was similar in both groups (86.9% versus 84.5%). However, oocyte maturation rate per collected oocyte was significantly higher for oocytes matured before vitrification (group 1, 46%) than for oocytes vitrified before IVM (group 2, 23.8%) (p < 0.01). Consequently, the number of MII oocytes inseminated per oocyte collected was significantly higher for group 1 (40%) than for group 2 (23.8%) (p < 0.05).
  
  
  CONCLUSIONS
  IVM procedure is more efficient when it is performed before oocyte vitrification.
authors.affiliation: Research Laboratory on Human Reproduction, Medicine Faculty, Université Libre de Bruxelles, Belgium, Campus Erasme, Brussels, Belgium. Giovanna.Fasano@erasme.ulb.ac.be
authors.forename: Giovanna
authors.initials: G
authors.lastname: Fasano
authors.forename: Isabelle
authors.initials: I
authors.lastname: Demeestere
authors.forename: Yvon
authors.initials: Y
authors.lastname: Englert
mesh_terms: D001755:Blastocyst / Q000502:physiology; D002470:Cell Survival; D002478:Cells, Cultured; D015925:Cryopreservation / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008677:Metaphase; D009865:Oocytes / Q000502:physiology*; D058989:Vitrification