title: Factors affecting the success of human blastocyst development and pregnancy following in vitro fertilization and embryo transfer.
abstract: OBJECTIVE
  To determine the factors affecting blastocyst development and pregnancy after IVF and ET.
  
  
  METHODS
  Retrospective analysis of data arising from a clinical trial.
  
  
  METHODS
  Private in vitro fertilization clinic.
  
  
  METHODS
  Fifty-six patients aged < or = 40 years, undergoing IVF procedures for infertility, recruited specifically for blastocyst transfer.
  
  
  METHODS
  All zygotes were cultured to days 5 or 6 after insemination, and one to four of the most advanced blastocysts were transferred to the patient's uterus.
  
  
  METHODS
  Development of zygotes to blastocysts in vitro and pregnancy and implantation rates after ET.
  
  
  RESULTS
  Fifty-one percent of all zygotes developed to blastocysts. Significant positive correlation between the number of blastocysts formed was observed with the number of oocytes, pronuclear zygotes, and eight-cell embryos formed. There was a negative correlation with male factor infertility. By day 5 or 6, 93% of the patients had at least one blastocysts, and the clinical pregnancy rate per transfer was 43% and the implantation per embryo transferred was 25%. No other clinical factor significantly affected the number of blastocysts formed, pregnancy rate, or implantation rate.
  
  
  CONCLUSIONS
  The numbers of oocytes, zygotes, and normally developing embryos in culture significantly affects the production of blastocysts in vitro. Male infertility significantly reduces blastocyst production. The number and the quality of the blastocysts transferred significantly influences clinical pregnancy rate.
authors.affiliation: Centre for Early Human Development, Monash University, Institute of Reproduction and Development, Clayton, Victoria, Australia. gayle.jones@med.monash.edu.au
authors.forename: G M
authors.initials: GM
authors.lastname: Jones
authors.forename: A O
authors.initials: AO
authors.lastname: Trounson
authors.forename: N
authors.initials: N
authors.lastname: Lolatgis
authors.forename: C
authors.initials: C
authors.lastname: Wood
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D008423:Maternal Age; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D018566:Pregnancy, High-Risk; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome