title: Closed vitrification of human oocytes and blastocysts: outcomes from a series of clinical cases.
abstract: OBJECTIVE
  High survival rates and clinical outcomes similar to those from fresh oocytes and blastocysts have been observed with open oocyte vitrification systems. It has been suggested that the extremely fast cooling rates that are only achieved with open systems are necessary for human oocyte and blastocyst vitrification. However, there is a potential risk of introducing contamination with open systems. The aim of this study was to assess whether similar survival and subsequent implantation rates could be achieved using a closed vitrification system for human oocytes and blastocysts.
  
  
  METHODS
  Initially, donated immature oocytes that were matured in vitro were vitrified using the cryoprotectants ethylene glycol (EG) + dimethyl sulphoxide (DMSO) + sucrose and either a closed system (Rapid-i®) or an open system (Cryolock). The closed system was subsequently introduced clinically for mature oocyte cryopreservation cases and blastocyst vitrification.
  
  
  RESULTS
  Using in vitro matured oocytes, a similar survival was achieved with the open system of 92.4 % (73/79) and with the closed system of 89.7 % (35/39). For clinical oocyte closed vitrification, high survival rate of 90.5 % (374/413) and an implantation rate of 32.7 % (18/55) from the transfer of day 2 embryos was achieved, which is similar to fresh day 2 embryo transfers. Blastocysts have also been successfully cryopreserved using the Rapid-i closed vitrification system with 94 % of blastocysts having an estimated ≥75 % of cells intact and a similar implantation rate (31.5 %) to fresh single blastocyst transfers.
  
  
  CONCLUSIONS
  Closed vitrification can achieve high survival and similar implantation rates to fresh for both oocytes and blastocysts.
authors.affiliation: Reproductive Services and Melbourne IVF, Royal Women's Hospital, Parkville, Victoria, Australia. debra.gook@mivf.com.au.|Department of Obstetrics and Gynaecology, University of Melbourne, Parkville, Victoria, Australia. debra.gook@mivf.com.au.
authors.forename: Debra A
authors.initials: DA
authors.lastname: Gook
authors.affiliation: Reproductive Services and Melbourne IVF, Royal Women's Hospital, Parkville, Victoria, Australia.
authors.forename: Boon
authors.initials: B
authors.lastname: Choo
authors.affiliation: Reproductive Services and Melbourne IVF, Royal Women's Hospital, Parkville, Victoria, Australia.
authors.forename: Harold
authors.initials: H
authors.lastname: Bourne
authors.affiliation: Reproductive Services and Melbourne IVF, Royal Women's Hospital, Parkville, Victoria, Australia.
authors.forename: Kelly
authors.initials: K
authors.lastname: Lewis
authors.affiliation: Reproductive Services and Melbourne IVF, Royal Women's Hospital, Parkville, Victoria, Australia.|Department of Obstetrics and Gynaecology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: David H
authors.initials: DH
authors.lastname: Edgar
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000008:administration & dosage; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D059471:In Vitro Oocyte Maturation Techniques; D018587:Oocyte Donation; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development*; D011247:Pregnancy; D018873:Pregnancy Rate; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents
keywords: Births; Blastocyst; Closed vitrification; Human; Implantation rate; Oocyte