title: Single-blastocyst transfer decreases twin gestation without affecting pregnancy outcome.
abstract: OBJECTIVE
  To compare the respective pregnancy outcomes of cycles undergoing fresh elective single-blastocyst transfer (eSBT) and double-blastocyst transfer (DBT) after IVF.
  
  
  METHODS
  Retrospective medical record review.
  
  
  METHODS
  Academic medical center.
  
  
  METHODS
  Couples undergoing fresh blastocyst transfer after IVF.
  
  
  METHODS
  One thousand, four hundred, ninety-nine consecutive IVF cycles from January 1, 2002 through March 31, 2006 at the Massachusetts General Hospital Fertility Center were reviewed. Patients undergoing fresh blastocyst transfer (eSBT, n = 52; DBT, n = 187) were identified.
  
  
  METHODS
  Respective pregnancy outcomes and the trend in twin gestations in all cycles undergoing blastocyst transfer, before and after the introduction of the eSBT program.
  
  
  RESULTS
  Statistically similar rates of biochemical pregnancy (76.9% vs. 77.6%), clinical pregnancy (61% vs. 63.4%), live birth (53.8% vs. 54.4%), and pregnancy loss (20% vs. 18.6%) per embryo transfer were observed for fresh eSBT and DBT cycles, respectively. Twin rates for eSBT were statistically significantly lower than for DBT cycles (3.1% vs. 51%). Fresh eSBT and DBT cryopreserved 2.8 vs. 1.7 blastocysts per cycle, respectively. Twenty-four months after the start of eSBT, the twin rate per transfer for all cycles undergoing blastocyst transfer (1, 2, or 3 blastocysts) was statistically significantly reduced from 47.2% to 22.9%, whereas the twin rate per transfer for all embryo transfers in women younger than 35 years of age was statistically significantly reduced from 28.8% to 15.6%.
  
  
  CONCLUSIONS
  Given the promising potential of eSBT to markedly reduce the risk of twin gestation without a significant compromise to pregnancy outcomes, an active attempt should be made to consider and use eSBT in the young, favorable-prognosis patient who has good-quality embryos available for transfer and cryopreservation.
authors.affiliation: The Fertility Center, Vincent Memorial Obstetrics and Gynecology Service, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA. astyer@partners.org
authors.forename: Aaron K
authors.initials: AK
authors.lastname: Styer
authors.forename: Diane L
authors.initials: DL
authors.lastname: Wright
authors.forename: Anne M
authors.initials: AM
authors.lastname: Wolkovich
authors.forename: Christine
authors.initials: C
authors.lastname: Veiga
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Toth
mesh_terms: D000328:Adult; D004624:Embryo Transfer / Q000379:methods*; D004958:Estradiol / Q000097:blood; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007231:Infant, Newborn; D007247:Infertility, Female / Q000145:classification; D008297:Male; D010053:Ovary / Q000502:physiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D038522:Twinning, Monozygotic / Q000502:physiology*; D014427:Twins
chemical_list: D004958:Estradiol; D005640:Follicle Stimulating Hormone