title: Adverse pregnancy outcomes after in vitro fertilization: effect of number of embryos transferred and plurality at conception.
abstract: OBJECTIVE
  To evaluate risks for adverse pregnancy outcomes by number of embryos transferred (ET) and fetal heartbeats (FHB) in assisted reproductive technology-conceived singleton live births.
  
  
  METHODS
  Longitudinal cohort using cycles reported to the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System between 2004 and 2008 among women who were treated and gave birth in Massachusetts.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Assisted reproductive technology data on 6,073 births between 2004 and 2008 were linked to vital records and hospital data. Likelihood of ET ≥3 vs. 1-2, FHB >1 vs. 1, and risks of preterm birth (PTB, <37 weeks' gestation), low birth weight (LBW, <2,500 g), and small-for-gestational-age birth weight (SGA, <10th percentile) with FHB >1 were modeled with binary logistic regression using a backward-stepping algorithm, and presented as adjusted odds ratios (95% confidence intervals).
  
  
  METHODS
  None.
  
  
  METHODS
  ET ≥3, FHB >1, PTB, LBW, and SGA.
  
  
  RESULTS
  Higher ET was significantly more likely with older maternal age, intracytoplasmic sperm injection, assisted hatching, cleavage-stage embryos, and thawed embryos. The likelihood of FHB >1 with ≥3 ET vs. 1-2 ET was 2.04 (1.68-2.48). Risks of PTB and LBW with FHB >1 were 1.63 (1.27-2.09) and 1.81 (1.36-2.39), respectively; the risk of SGA was not significant. Nulliparity was associated with higher risks of PTB (1.34 [1.12-1.59]), LBW (1.48 [1.20-1.83]), and SGA (2.17 [1.69-2.78]).
  
  
  CONCLUSIONS
  Number of embryos transferred was strongly associated with FHBs, with twice the risk of FHB >1 with ≥3 ET vs. 1-2 ET. Increasing FHBs were associated with significantly greater risks for PTB and LBW outcomes.
authors.affiliation: Department of Obstetrics, Gynecology, and Reproductive Biology, Michigan State University, East Lansing, Michigan. Electronic address: lukeb@msu.edu.
authors.forename: Barbara
authors.initials: B
authors.lastname: Luke
authors.affiliation: Department of Obstetrics and Gynecology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire.
authors.forename: Judy E
authors.initials: JE
authors.lastname: Stern
authors.affiliation: MassGeneral Hospital for Children, Harvard Medical School, Boston, Massachusetts.
authors.forename: Milton
authors.initials: M
authors.lastname: Kotelchuck
authors.affiliation: Department of Community Health Sciences, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Eugene R
authors.initials: ER
authors.lastname: Declercq
authors.affiliation: Department of Obstetrics and Gynecology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hornstein
authors.affiliation: Department of Community Health Sciences, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Daksha
authors.initials: D
authors.lastname: Gopal
authors.affiliation: Department of Community Health Sciences, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Lan
authors.initials: L
authors.lastname: Hoang
authors.affiliation: Massachusetts Department of Public Health, Boston, Massachusetts.
authors.forename: Hafsatou
authors.initials: H
authors.lastname: Diop
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004624:Embryo Transfer / Q000009:adverse effects* / Q000379:methods / Q000639:trends; D005260:Female; D005306:Fertilization / Q000502:physiology; D005307:Fertilization in Vitro / Q000009:adverse effects* / Q000379:methods / Q000639:trends; D006801:Humans; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D010298:Parity / Q000502:physiology; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012189:Retrospective Studies
keywords: Assisted reproductive technology; birth outcomes; embryos transferred; fetal heartbeats