title: Impact of the size of zona pellucida thinning area on vitrified-warmed cleavage-stage embryo transfers: a prospective, randomized study.
abstract: OBJECTIVE
  The aim of this study was to determine if the size of zona pellucida thinning area by laser assisted hatching could affect the rates of pregnancy and implantation for vitrified-warmed embryo transfers at the cleavage-stage.
  
  
  METHODS
  A total of 120 vitrified-warmed cleavage-stage embryo transfers were randomly assigned to either quarter or half of zona pellucida thinning group.
  
  
  RESULTS
  The rates of clinical pregnancy (46.7 versus 25.0%) and implantation (32.0 versus 16.2%) were significantly greater in the half thinning group than in the quarter thinning group (P = 0.0218 and P = 0.0090, respectively).
  
  
  CONCLUSIONS
  The results of this investigation show that, in vitrified-warmed embryo transfers at the cleavage-stage, the size of zona pellucida thinning area by laser assisted hatching impacts the rate of clinical pregnancy and implantation and that half of zona pellucida thinning significantly increases both of these results compared with quarter of zona pellucida thinning.
authors.affiliation: Kinutani Women's Clinic, 8-23-4F, Hondori, Naka-ku, Hiroshima 730-0035, Japan. hiraoka@chive.ocn.ne.jp
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Hiraoka
authors.forename: Kaori
authors.initials: K
authors.lastname: Hiraoka
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Horiuchi
authors.forename: Tomoyo
authors.initials: T
authors.lastname: Kusuda
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Okano
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kinutani
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kinutani
mesh_terms: D000328:Adult; D001757:Blastomeres / Q000502:physiology*; D015925:Cryopreservation; D010064:Embryo Implantation / Q000502:physiology*; D004624:Embryo Transfer / Q000379:methods*; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007834:Lasers; D011247:Pregnancy; D018873:Pregnancy Rate; D016896:Treatment Outcome; D015044:Zona Pellucida / Q000502:physiology / Q000528:radiation effects