title: Vitrification demonstrates significant improvement versus slow freezing of human blastocysts.
abstract: Blastocyst culture has reduced the number of embryos transferred per cycle, whilst simultaneously creating new quandaries regarding supernumerary blastocyst cryopreservation. This retrospective study was undertaken to compare a slow freezing protocol to a vitrification protocol for cryopreservation of day 5 and day 6 human blastocysts. To demonstrate this, the survival, implantation rate and pregnancy rates were compared after thawing, assessment and embryo transfer of 86 consecutive day 5 and day 6 thawed blastocyst transfer cycles from January 1, 2002 to December 31, 2003. Seventy-one day 5 slow-frozen (SF) blastocysts were thawed and 59 embryos survived the thawing (83.1%). An average of 2.5 SF blastocysts was replaced per embryo transfer, resulting in a pregnancy rate of 16.7% (4/24). Concurrently, 41 vitrified (VIT) blastocysts were thawed and all 41 survived the thawing process (100%). An average of 2.0 VIT blastocysts was replaced per embryo transfer, resulting in a pregnancy rate of 50% (10/20). Survival, pregnancy and implantation rates of day 5 VIT blastocysts have significantly increased (P < 0.01, P < 0.02 and P < 0.01 respectively) over day 5 SF blastocysts. A similar trend was observed with day 6 blastocysts.
authors.affiliation: Advanced Institute of Fertility, 2800 West Kinnickinnic River Parkway, Milwaukee, WI 53233, USA.
authors.forename: Ed
authors.initials: E
authors.lastname: Stehlik
authors.forename: Joni
authors.initials: J
authors.lastname: Stehlik
authors.forename: K Paul
authors.initials: KP
authors.lastname: Katayama
authors.forename: Masashige
authors.initials: M
authors.lastname: Kuwayama
authors.forename: Varya
authors.initials: V
authors.lastname: Jambor
authors.forename: Rebecca
authors.initials: R
authors.lastname: Brohammer
authors.forename: Osama
authors.initials: O
authors.lastname: Kato
mesh_terms: D001755:Blastocyst / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D005615:Freezing; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies