title: Transferring more embryos increases risk of heterotopic pregnancy.
abstract: OBJECTIVE
  To analyze symptoms and signs that may distinguish heterotopic pregnancy from solely ectopic pregnancy (EP) after IVF. To determine if the number of embryos transferred is a risk factor for heterotopic compared with solely EP.
  
  
  METHODS
  Retrospective cohort of 587 IVF pregnancies, 328 with distorted tubal anatomy.
  
  
  METHODS
  University Hospital, London, a referral center for Ontario provincial government-supported assisted reproductive technologies.
  
  
  METHODS
  Couples undergoing IVF.
  
  
  METHODS
  None.
  
  
  METHODS
  Heterotopic pregnancy, solely EP, intrauterine pregnancy, and distorted pelvic anatomy.
  
  
  RESULTS
  Of 587 pregnancies, 7 were heterotopic pregnancies and 24 were solely EP, all in the subset of 328 women with distorted tubal anatomy. Symptoms, signs and time of diagnosis were not different between heterotopic and solely ectopic gestations. Compared with solely EP, heterotopic pregnancies were associated with transfer of more embryos. With four or more embryos transferred, the odds ratio for development of heterotopic versus solely ectopic gestation was 10.0.
  
  
  CONCLUSIONS
  Heterotopic pregnancy occurred in 2% of gestations after IVF, all in women with distorted tubal anatomy. Transfer of four or more embryos was a risk factor for heterotopic pregnancy.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Western Ontario, London, Canada.
authors.forename: I S
authors.initials: IS
authors.lastname: Tummon
authors.forename: N A
authors.initials: NA
authors.lastname: Whitmore
authors.forename: S A
authors.initials: SA
authors.lastname: Daniel
authors.forename: J A
authors.initials: JA
authors.lastname: Nisker
authors.forename: A A
authors.initials: AA
authors.lastname: Yuzpe
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003937:Diagnosis, Differential; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000175:diagnosis / Q000453:epidemiology*; D012189:Retrospective Studies; D012307:Risk Factors