title: The births of five Spanish babies from cryopreserved donated oocytes.
abstract: BACKGROUND
  The technique of freezing oocytes is still not widely used. Reasons cited for this include the technique's low efficacy and the risk of aneuploidy. However, the introduction of technical changes (the type and concentration of cryoprotective substances; slow freezing and rapid thawing; and fertilization by ICSI) has led to improved results. We present four pregnancies obtained using mature oocytes (in metaphase II) that had been frozen and thawed. The oocytes were donated by young women who were not patients.
  
  
  METHODS
  The frozen oocytes (n = 88) came from seven donors aged 18-25 years. The metaphase II oocytes, morphologically normal in appearance, were denuded of their cumulus-corona complex. The cryoprotective freezing solution contained 1,2-propanediol (1.5 mol/l) and sucrose (0.3 mol/l). Freezing was slow and thawing rapid. The oocytes were fertilized by ICSI.
  
  
  RESULTS
  Seventy-nine of the 88 thawed oocytes survived (89.8%); 58 were fertilized (73.4% of all those microinjected); and 26 were transferred (44.8% of all those fertilized). Four pregnancies were produced after seven transfers (57.1%). Five children were born from four pregnancies.
  
  
  CONCLUSIONS
  With the freezing/thawing technique used, oocyte survival was high ( approximately 90%). The pregnancy rate with frozen oocytes was similar to that obtained using fresh oocytes from donors ( approximately 50%).
authors.affiliation: Instituto de Reproducción CEFER, Marquesa de Vilallonga 12, 08017 Barcelona, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Fosas
authors.forename: F
authors.initials: F
authors.lastname: Marina
authors.forename: P J
authors.initials: PJ
authors.lastname: Torres
authors.forename: I
authors.initials: I
authors.lastname: Jové
authors.forename: P
authors.initials: P
authors.lastname: Martín
authors.forename: N
authors.initials: N
authors.lastname: Pérez
authors.forename: N
authors.initials: N
authors.lastname: Arnedo
authors.forename: S
authors.initials: S
authors.lastname: Marina
mesh_terms: D000328:Adult; D002470:Cell Survival; D015925:Cryopreservation; D003451:Cryoprotective Agents; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D008677:Metaphase; D008875:Middle Aged; D009865:Oocytes / Q000166:cytology*; D011247:Pregnancy; D011256:Pregnancy Outcome; D012661:Semen; D013030:Spain; D020554:Sperm Injections, Intracytoplasmic
chemical_list: D003451:Cryoprotective Agents