title: A novel method to evaluate pregnancy rates following in vitro fertilization to enable a better understanding of the true efficacy of the procedure.
abstract: OBJECTIVE
  To propose a new method of evaluating in vitro fertilization (IVF)-embryo transfer (ET) outcome so that statistics are not biased against IVF centers that have strong cryopreservation programs.
  
  
  METHODS
  A retrospective review was made of all patients undergoing IVF-ET in a four and a half year time period having at least two embryos transferred. There were no other exclusions. All types of problems and controlled ovarian hyperstimulation protocols were used. Data were analyzed according to four age groups: < or =35, 36-39, 40-42, > or =43. Pregnancy rates were calculated according to a given oocyte harvest where a pregnancy was counted if the woman conceived on the fresh transfer or any succeeding frozen ET from embryos obtained from oocytes retrieved on that harvest. Also pregnancy rates per transfer and retrieval were evaluated.
  
  
  RESULTS
  For women < or =35 to age 39 the new category of clinical pregnancy rate per oocyte harvest was significantly higher than the pregnancy rate per transfer. The pregnancy rate per transfer was significantly higher than the pregnancy rate per retrieval in women up to age 42.
  
  
  CONCLUSIONS
  We propose that calculating pregnancy rate per harvest is the best method to evaluate the true efficacy of IVF-ET especially from programs with a strong emphasis on cryopreservation.
authors.forename: B
authors.initials: B
authors.lastname: Katsoff
authors.forename: J H
authors.initials: JH
authors.lastname: Check
authors.forename: J K
authors.initials: JK
authors.lastname: Choe
authors.forename: C
authors.initials: C
authors.lastname: Wilson
mesh_terms: D000328:Adult; D017677:Age Distribution; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000706:statistics & numerical data*; D006801:Humans; D008875:Middle Aged; D009865:Oocytes; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010062:Ovulation Induction; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies