title: Elective single embryo transfer and perinatal outcomes: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To determine whether elective single embryo transfer (eSET) lowers the risk of poor perinatal outcomes associated with IVF, when [1] compared with double embryo transfer (DET) or multiple embryo transfer (MET), and separately, [2] compared with spontaneous conceptions.
  
  
  METHODS
  Systematic review and meta-analysis.
  
  
  METHODS
  Centers for reproductive care.
  
  
  METHODS
  Infertility patients.
  
  
  METHODS
  MEDLINE, Embase, and bibliographies were searched for the period 1978-2011. Two reviewers independently assessed titles, abstracts, and full studies, extracted data, and assessed quality. Dichotomous data were pooled using relative risks and continuous data with mean differences using a random effects model. Randomized controlled trials (RCTs), case-control studies, and cohort studies that examined any of the primary or secondary outcomes in singleton, twin, or multiple-order infants conceived by eSET as compared with [1] those conceived by DET or MET or [2] spontaneously conceived singleton gestations were included.
  
  
  METHODS
  Primary outcomes were preterm birth (PTB, <37 weeks' gestation) and low birth weight (LBW, <2,500 g).
  
  
  RESULTS
  Sixteen studies were included (eight RCTs, eight cohort studies). Compared with DET-conceived infants, eSET-conceived singletons were less likely to be born either preterm (RCT-based relative risk [RR] 0.37, 95% confidence interval [CI] 0.25-0.55) or with LBW (RCT-based RR 0.25, 95% CI 0.15-0.45; cohort study RR 0.51, 95% CI 0.29-0.91). However, compared with spontaneously conceived singletons, eSET gestations had higher risks of PTB (RR 2.13, 95% CI 1.26-3.61), placenta previa (RR 6.02, 95% CI 2.79-13.01), gestational diabetes (RR 1.69, 95% CI 1.19-2.42), and ectopic pregnancy (RR 6.40, 95% CI 4.38-9.35).
  
  
  CONCLUSIONS
  Elective single embryo transfer is associated with decreased risks of PTB and LBW compared with DET but higher risks of PTB compared with spontaneously conceived singletons.
authors.affiliation: Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Rosheen
authors.initials: R
authors.lastname: Grady
authors.forename: Nika
authors.initials: N
authors.lastname: Alavi
authors.forename: Rachel
authors.initials: R
authors.lastname: Vale
authors.forename: Mohammad
authors.initials: M
authors.lastname: Khandwala
authors.forename: Sarah D
authors.initials: SD
authors.lastname: McDonald
mesh_terms: D005260:Female; D005307:Fertilization in Vitro; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007234:Infant, Premature; D007246:Infertility / Q000503:physiopathology / Q000628:therapy*; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000209:etiology; D018570:Risk Assessment; D012307:Risk Factors; D056826:Single Embryo Transfer / Q000009:adverse effects; D016896:Treatment Outcome