title: Three years of routine vitrification of human zygotes: is it still fair to advocate slow-rate freezing?
abstract: Cryopreservation of human oocytes and embryos is a necessary tool in assisted reproduction treatment that leads to an increased cumulative outcome while decreasing costs. Vitrification is a cryopreservation technique that leads to a glass-like solidification, with rapid cooling of cells or tissues. Nowadays vitrification is claimed to be the future of cryopreservation of human embryos due to improved survival rates and clinical outcomes. This study was conducted at a university clinic to assess the safety and efficiency of vitrification of human zygotes as a routine procedure. A total of 849 pronuclear-stage (PN) zygotes were vitrified between March 2004 and July 2006. During this period, 103 cycles of cryopreserved embryo transfer were completed. In total, 339 PN zygotes were thawed resulting in an 89% survival rate (302 PN zygotes). The mean number of embryos per transfer was 2.2. The pregnancy rate obtained was three times higher (36.9%) than that obtained with the slow-rate freezing method (10.2%) used previously in the same centre. In conclusion, vitrification of human zygotes at the pronuclear stage seems to be a successful and reliable method with favourable outcomes and can be recommended as a routine technique for cryopreservation of human embryos.
authors.affiliation: University of Schleswig-Holstein, Department of Gynaecology and Obstetrics, Reproductive Medicine Unit, University of Lübeck, Ratzeburger Allee 160, 23560 Lübeck, Germany. sf_alhasani@hotmail.com
authors.forename: Safaa
authors.initials: S
authors.lastname: Al-Hasani
authors.forename: Batuhan
authors.initials: B
authors.lastname: Ozmen
authors.forename: Nikoleta
authors.initials: N
authors.lastname: Koutlaki
authors.forename: Beate
authors.initials: B
authors.lastname: Schoepper
authors.forename: Klaus
authors.initials: K
authors.lastname: Diedrich
authors.forename: Askan
authors.initials: A
authors.lastname: Schultze-Mosgau
mesh_terms: D000328:Adult; D015925:Cryopreservation / Q000295:instrumentation / Q000379:methods*; D003451:Cryoprotective Agents / Q000494:pharmacology; D004622:Embryo, Mammalian / Q000166:cytology* / Q000473:pathology; D005260:Female; D005615:Freezing; D006801:Humans; D007246:Infertility / Q000628:therapy*; D008297:Male; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D010053:Ovary / Q000473:pathology; D011247:Pregnancy; D011256:Pregnancy Outcome; D016896:Treatment Outcome; D015053:Zygote / Q000166:cytology
chemical_list: D003451:Cryoprotective Agents