title: Impact of elective single embryo transfer on the twin pregnancy rate.
abstract: BACKGROUND
  It is unclear how the implementation of elective single embryo transfer in clinical practice would affect clinical pregnancy and delivery rates and multiple birth rates.
  
  
  METHODS
  This retrospective study analysed 1871 IVF/ICSI cycles carried out from 1997 to 2001 in the IVF programme of a single university infertility clinic.
  
  
  RESULTS
  The number of elective single embryo transfers increased from 11 to 56%. At the same time the clinical pregnancy rate was relatively stable; mean 34.0% (range 28-42). The number of embryos per embryo transfer decreased from 1.8 to 1.3. The multiple pregnancy and delivery rates dropped markedly from 25 to 7.5% and from 25 to 5% respectively.
  
  
  CONCLUSIONS
  An elective single embryo transfer programme can be adopted in daily practice that decreases the twinning rate to <10% and does not affect the overall pregnancy rate.
authors.affiliation: Department of Obstetrics and Gynaecology, Helsinki University Central Hospital, P.O.Box 140, 00029 HUS, Finland. aila.tittinen@hus.fi
authors.forename: A
authors.initials: A
authors.lastname: Tiitinen
authors.forename: L
authors.initials: L
authors.lastname: Unkila-Kallio
authors.forename: M
authors.initials: M
authors.lastname: Halttunen
authors.forename: C
authors.initials: C
authors.lastname: Hyden-Granskog
mesh_terms: D000328:Adult; D004624:Embryo Transfer / Q000706:statistics & numerical data*; D005260:Female; D005307:Fertilization in Vitro / Q000706:statistics & numerical data*; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic / Q000706:statistics & numerical data; D014427:Twins / Q000706:statistics & numerical data*