title: Relationship between interpregnancy interval and birth defects in Washington State.
abstract: OBJECTIVE
  Interpregnancy interval (IPI) influences numerous adverse perinatal outcomes. IPI's impact on birth defects is unclear.
  
  
  METHODS
  We conducted a population-based case-control study, using 1998 to 2008 administrative data from Washington State. A total of 10, 772 cases, women whose second of two births resulted in an infant with a birth defect, were compared with 32 ,310 controls, women whose second of two births did not result in an infant with a birth defect.
  
  
  RESULTS
  Compared with mothers with an IPI between 18 to 23 months, those with an IPI <6 months or ≥60 months had elevated risks of delivering an infant with a birth defect (odds ratio=1.15, 95% confidence interval: 1.03 to 1.28, and odds ratio=1.15, 95% confidence interval: 1.04 to 1.26, respectively).
  
  
  CONCLUSIONS
  We observed a J-shaped relationship between IPI and risk of having an infant with a birth defect. As this is one of the first studies to evaluate this association, confirmatory studies are needed.
authors.affiliation: Department of Surgery, University of Washington, Seattle, WA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Kwon
authors.forename: M
authors.initials: M
authors.lastname: Lazo-Escalante
authors.forename: M V
authors.initials: MV
authors.lastname: Villaran
authors.forename: C I
authors.initials: CI
authors.lastname: Li
mesh_terms: D000328:Adult; D001721:Birth Intervals / Q000706:statistics & numerical data*; D016022:Case-Control Studies; D000013:Congenital Abnormalities / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D012307:Risk Factors; D014861:Washington / Q000453:epidemiology; D055815:Young Adult