title: Obligatory versus elective single embryo transfer in in vitro fertilization. A population-based analysis of data from the U.K. Human Fertilisation and Embryology Authority.
abstract: OBJECTIVE
  To determine how obligatory single embryo transfer (SET) and elective SET influence pregnancy outcome.
  
  
  METHODS
  We compared women who underwent obligatory and elective SET using data from a comprehensive, population-based register from the United Kingdom Human Fertilisation and Embryology Authority, which contained all in vitro fertilization (IVF) treatments administered between 1991 and 1998. Generalized estimating equations were used to generate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) to compare clinical pregnancy, live birth, and multiple birth rates.
  
  
  RESULTS
  Obligatory and elective SET had similar clinical pregnancy and live birth rates and comparable multiple birth rates. Obligatory and elective SET were equally likely to end in a live birth (OR = 1.08; 95% CI = 0.90, 1.30). Similar results were found after restricting the data to women without previous IVF births (OR = 1.18; 95% CI = 0.98, 1.42) and without previous naturally conceived live births (OR = 1.16; 95% CI = 0.95, 1.43).
  
  
  CONCLUSIONS
  This study suggests that obligatory SET can achieve pregnancy and live birth rates that are at least as good as elective SET. Equally important is the low multiple birth rate which was maintained in both forms of SET. More studies comparing elective versus obligatory SET can assist with achieving optimal pregnancy rates while preventing multiple births.
authors.affiliation: Department of Family Medicine and Public Health Sciences, Wayne State University School of Medicine, 3939 Woodward Avenue, Room 322, Detroit, MI 48201, USA. jstraug@med.wayne.edu
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Straughen
authors.forename: Hamisu M
authors.initials: HM
authors.lastname: Salihu
authors.forename: Louis
authors.initials: L
authors.lastname: Keith
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Petrozzino
authors.forename: Christopher
authors.initials: C
authors.lastname: Jones
mesh_terms: D000328:Adult; D016001:Confidence Intervals; D005260:Female; D005306:Fertilization; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D050498:Live Birth; D016017:Odds Ratio; D011247:Pregnancy; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D012042:Registries; D056826:Single Embryo Transfer / Q000379:methods*; D006113:United Kingdom