title: Developmental potential of zona pellucida-free oocytes obtained following mild in vitro fertilization.
abstract: OBJECTIVE
  To determine the developmental potential of oocytes in which the zona pellucida was damaged and subsequently removed, producing "zona-free" (ZF) oocytes that were cultured until the blastocyst stage.
  
  
  METHODS
  ZF eggs from cycles with more than one oocytes retrieved (n = 97) were compared with zona-intact (ZI) oocytes originating from the same patient.
  
  
  METHODS
  Private infertility clinic.
  
  
  METHODS
  Infertile patients (n = 135) undergoing minimal ovarian stimulation or natural-cycle in vitro fertilization treatment during 2010-2012.
  
  
  METHODS
  ZF oocytes undergoing intracytoplasmic sperm injection (ICSI) fertilization, blastocyst culture, elective vitrification, and subsequent single vitrified-thawed blastocyst transfer (SVBT).
  
  
  METHODS
  Rate of fertilization, cleavage, and blastocyst development. Live birth rate and neonatal outcome in subsequent SVBT cycles.
  
  
  RESULTS
  There were no significant differences in fertilization (77% vs. 77%), cleavage (75% vs. 75%), or blastocyst development rates (39% vs. 32%) between the internally controlled ZF and ZI groups, respectively. Survival after thawing (90% vs. 100%) and live birth rates (37% vs. 36%) per thawed blastocyst were also similar. Newborns originating from all ZF and ZI oocytes had a similar gestational age at delivery (38.3 ± 3.7 wk vs. 39.5 ± 1.5 wk) and birth weight (3,115 ± 946 g vs. 3,010 ± 441 g).
  
  
  CONCLUSIONS
  Our retrospective comparative study suggests that ZF eggs could be as successfully fertilized and cultured until the blastocyst stage as ZI control eggs without adversely affecting subsequent pregnancy rates and basic neonatal outcome.
authors.affiliation: Kato Ladies Clinic, Tokyo, Japan. Electronic address: scsosob@gmail.com.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ueno
authors.affiliation: Kobe Motomachi Yume Clinic, Kobe, Japan.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bodri
authors.affiliation: Kato Ladies Clinic, Tokyo, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Uchiyama
authors.affiliation: Kato Ladies Clinic, Tokyo, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Okimura
authors.affiliation: Kato Ladies Clinic, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okuno
authors.affiliation: Kato Ladies Clinic, Tokyo, Japan.
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Kato Ladies Clinic, Tokyo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kato
mesh_terms: D000328:Adult; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D054315:Oocyte Retrieval / Q000379:methods; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D012189:Retrospective Studies; D056826:Single Embryo Transfer / Q000379:methods; D020554:Sperm Injections, Intracytoplasmic; D058989:Vitrification; D015044:Zona Pellucida / Q000502:physiology*
keywords: Zona pellucida; blastocyst culture; in vitro fertilization; minimal ovarian stimulation