title: Ectopic pregnancy after in vitro fertilization: differences between fresh and frozen-thawed cycles.
abstract: OBJECTIVE
  To evaluate whether the uterine environment is associated with the risk of ectopic implantation by comparing outcomes of fresh and frozen-thawed embryo transfers.
  
  
  METHODS
  Retrospective historical cohort.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  We used the Society for Assisted Reproductive Technologies (SART) database to identify pregnancies that resulted from fresh and frozen blastocyst transfers from 2008 to 2011.
  
  
  METHODS
  None.
  
  
  METHODS
  We determined the proportion of ectopic (EP) versus intrauterine-only pregnancies resulting from fresh or frozen embryo transfers in autologous and donor-oocyte cycles. Generalized estimation equation regression models were used to adjust for maternal and treatment characteristics.
  
  
  RESULTS
  Among 103,070 cycles that resulted in a clinical pregnancy, 1.38% were ectopic. The odds of EP were 65% lower in women who had a frozen compared with a fresh transfer in autologous cycles. Donor-oocyte transfers had lower odds of EP compared with autologous cycles, with no difference between fresh and frozen donor transfers. Women who had both a fresh and a frozen transfer with autologous oocytes had a higher risk of EP in their fresh cycles compared with their frozen cycles.
  
  
  CONCLUSIONS
  Embryo transfers in cycles without ovarian hyperstimulation, such as frozen or donor cycles, were associated with lower rates of EP compared with fresh autologous cycles, suggesting that a difference in the tubal-uterine environment contributes to abnormal implantation after IVF.
authors.affiliation: Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, Johns Hopkins University, Lutherville, Maryland. Electronic address: llondra1@jhmi.edu.
authors.forename: Laura
authors.initials: L
authors.lastname: Londra
authors.affiliation: Department of Population, Family, and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Moreau
authors.affiliation: Department of Population, Family, and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Donna
authors.initials: D
authors.lastname: Strobino
authors.affiliation: Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, Johns Hopkins University, Lutherville, Maryland.
authors.forename: Jairo
authors.initials: J
authors.lastname: Garcia
authors.affiliation: Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, Johns Hopkins University, Lutherville, Maryland.
authors.forename: Howard
authors.initials: H
authors.lastname: Zacur
authors.affiliation: Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, Johns Hopkins University, Lutherville, Maryland.
authors.forename: Yulian
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000328:Adult; D015331:Cohort Studies; D015925:Cryopreservation / Q000379:methods* / Q000639:trends*; D004624:Embryo Transfer / Q000009:adverse effects / Q000379:methods / Q000639:trends; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects / Q000379:methods* / Q000639:trends*; D006801:Humans; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000175:diagnosis / Q000453:epidemiology*; D012189:Retrospective Studies; D014019:Tissue Donors
keywords: Ectopic pregnancy; embryo transfer; in vitro fertilization; risk factors