title: Freeze-all at the blastocyst or bipronuclear stage: a randomized clinical trial.
abstract: OBJECTIVE
  To compare outcomes for patients randomized to have all embryos cryopreserved at the blastocyst stage or at the bipronuclear stage with subsequent post-thaw culture to the blastocyst stage.
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  Private fertility center.
  
  
  METHODS
  This study included 140 women, age 18-40 years, with at least eight antral follicles, and day 3 FSH <10 IU/L undergoing IVF.
  
  
  METHODS
  After oocyte retrieval, subjects were randomized to have entire embryo cohorts cryopreserved at either the bipronuclear stage (2PN Cryo group) or at the blastocyst stage (Blast Cryo group).
  
  
  METHODS
  Ongoing pregnancy (viable fetal heart motion at 10 weeks' gestation) per oocyte retrieval through the first transfer attempt.
  
  
  RESULTS
  No significant differences were observed between the two study groups in age at retrieval, body mass index, antral follicle count, day 3 FSH level, or IVF cycle parameters. No significant differences were observed in ongoing pregnancy rate per retrieval (62.0%; 95% confidence interval [CI], 50.3%-72.4%) in the 2PN Cryo group; and 55.1%; 95% CI, 42.6%-67.1% in the Blast Cryo group), implantation rate (60.0% vs. 62.7%), ongoing pregnancy rate per thaw (62.0% vs. 59.4%), ongoing pregnancy rate per transfer (67.7% vs. 69.1%), and the cumulative ongoing pregnancy rate per retrieval from all thaws to date of embryos derived from the study retrieval cycle (64.8% vs. 60.9%).
  
  
  CONCLUSIONS
  Freeze-all at the blastocyst stage or at the bipronuclear stage has similar efficacy and IVF outcomes. The choice between them may depend primarily on logistical factors.
  
  
  BACKGROUND
  NCT01247987.
authors.affiliation: Fertility Center of Las Vegas, Las Vegas, Nevada; Department of Obstetrics and Gynecology, University of Nevada School of Medicine, Las Vegas, Nevada. Electronic address: bsshapiro@aol.com.
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Shapiro
authors.affiliation: Fertility Center of Las Vegas, Las Vegas, Nevada; Department of Obstetrics and Gynecology, University of Nevada School of Medicine, Las Vegas, Nevada.
authors.forename: Said T
authors.initials: ST
authors.lastname: Daneshmand
authors.affiliation: Fertility Center of Las Vegas, Las Vegas, Nevada; Department of Obstetrics and Gynecology, University of Nevada School of Medicine, Las Vegas, Nevada.
authors.forename: Forest C
authors.initials: FC
authors.lastname: Garner
authors.affiliation: Fertility Center of Las Vegas, Las Vegas, Nevada.
authors.forename: Martha
authors.initials: M
authors.lastname: Aguirre
authors.affiliation: Fertility Center of Las Vegas, Las Vegas, Nevada.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Hudson
mesh_terms: D000293:Adolescent; D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D016009:Chi-Square Distribution; D015925:Cryopreservation; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D005260:Female; D005298:Fertility; D005307:Fertilization in Vitro / Q000009:adverse effects; D006801:Humans; D007246:Infertility / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D016015:Logistic Models; D009505:Nevada; D054315:Oocyte Retrieval; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D058989:Vitrification; D055815:Young Adult
keywords: In vitro fertilization; blastocyst transfer; embryo cryopreservation; embryo vitrification; frozen embryo transfer