title: Transfer of two embryos instead of three will not compromise pregnancy rate but will reduce multiple pregnancy rate in an assisted reproduction unit.
abstract: OBJECTIVE
  To compare the pregnancy rates and multiple pregnancy rates of cycles initiated in 1998 and in 1999, during which 3 and 2 embryos were advised to be replaced, respectively.
  
  
  METHODS
  A retrospective study
  
  
  RESULTS
  There were no differences between 1998 and 1999 in the pregnancy rate per cycle started or per transfer, implantation rate and the multiple pregnancy rates, despite a significantly lower number of embryos replaced in 1999. A significantly higher implantation rate was found in cycles with frozen embryos than those without. Using logistic regression analysis, the chance of pregnancy was significantly improved only by the presence of frozen embryos in the fresh cycles with an odds ratio of 2.0 (95% confidence interval: 1.3-3.0) whereas the chance of multiple pregnancy was significantly increased by replacing 3 embryos instead of 2 (odds ratio: 2.1, 95% confidence interval: 1.1-4.2).
  
  
  CONCLUSIONS
  Patients should be advised to have 2 embryos replaced without jeopardizing the pregnancy rates in the fresh cycles. The risk of multiple pregnancy is significantly increased when 3 embryos are transferred instead of 2.
authors.affiliation: Department of Obstetrics and Gynaecology, Queen Mary Hospital, The University of Hong Kong, PRC.
authors.forename: E H
authors.initials: EH
authors.lastname: Ng
authors.forename: E Y
authors.initials: EY
authors.lastname: Lau
authors.forename: W S
authors.initials: WS
authors.lastname: Yeung
authors.forename: P C
authors.initials: PC
authors.lastname: Ho
mesh_terms: D000328:Adult; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple; D012189:Retrospective Studies