title: Elective transfer of single fresh blastocysts and later transfer of cryostored blastocysts reduces the twin pregnancy rate and can improve the in vitro fertilization live birth rate in younger women.
abstract: OBJECTIVE
  To determine the extent to which embryo selection by blastulation and elective single blastocyst transfer, supported by efficient cryostorage of spare embryos, can reduce multiple pregnancies and maintain or improve on the live birth rate from IVF.
  
  
  METHODS
  Prospective, nonrandomized cohort study.
  
  
  METHODS
  Sydney IVF, a private clinic in Australia.
  
  
  METHODS
  In vitro fertilization patients aged <38 years with three or more usable blastocyst, recruited from April 2000 through December 2001, with pregnancies followed up until August 2004.
  
  
  METHODS
  Blastocysts were cultured and cryostored with stage-specific culture medium and low oxygen conditions.
  
  
  METHODS
  Fetal heart-positive twin pregnancy rate and accumulating "take-home baby" rate per retrieval leading to blastocyst transfer.
  
  
  RESULTS
  Among 121 women who elected single fresh blastocyst transfer (but who could elect to have two frozen blastocysts transferred at once), 79 (65.3%) took home a baby, with a twin pregnancy rate of 7%. Among 285 women who chose two blastocysts for fresh transfer, 184 (64.2%) took home at least one baby, with a twin pregnancy rate of 34% and five perinatal deaths.
  
  
  CONCLUSIONS
  With technically appropriate blastocyst culture and freezing, and elective single blastocyst transfer in the fresh cycle, the overall multiple pregnancy rate can be reduced by >75%, permitting in this series a slight increase in the chance of taking home a baby.
authors.affiliation: Sydney IVF, Sydney, New South Wales, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Henman
authors.forename: James W
authors.initials: JW
authors.lastname: Catt
authors.forename: Tina
authors.initials: T
authors.lastname: Wood
authors.forename: Mark C
authors.initials: MC
authors.lastname: Bowman
authors.forename: Kylie A
authors.initials: KA
authors.lastname: de Boer
authors.forename: Robert P S
authors.initials: RP
authors.lastname: Jansen
mesh_terms: D000328:Adult; D001757:Blastomeres / Q000166:cytology*; D015331:Cohort Studies; D015925:Cryopreservation; D004624:Embryo Transfer / Q000706:statistics & numerical data*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D011446:Prospective Studies; D014427:Twins