title: Duration of pregnancy, even at term, predicts long-term risk of coronary heart disease and stroke mortality in women: a population-based study.
abstract: OBJECTIVE
  Preterm delivery may predict an increased risk of cardiovascular disease in mothers, providing opportunities for prevention. No study had examined whether gestation length within the term period predicts future CVD, and there are few data segregating spontaneous from medically indicated deliveries.
  
  
  METHODS
  We used proportional hazards models to predict CVD death by gestation length, adjusted for age, education, and delivery year among 688,662 women with births from 1967 through 1998 in the Medical Birth Registry of Norway. Mothers were traced in the National Cause of Death Registry through 2009; there were 2324 CVD deaths.
  
  
  RESULTS
  Compared with women who delivered spontaneously at 39-41 weeks' gestation, women who spontaneously delivered earlier had higher risks of CVD death. Hazard ratios were 1.9 at 22-31 weeks, 2.2 at 32-34 weeks, 1.6 at 35-36 weeks, and 1.4 at 37-38 weeks. Risks were higher among women with medically indicated deliveries (hazard ratio, 4.8 at 22-31 weeks, 2.7 at 32-34 weeks, 4.3 at 35-36 weeks, and 1.6 at 37-38 weeks compared with spontaneous deliveries at 39-41 weeks). Neither spontaneous nor indicated delivery after 41 weeks was associated with CVD mortality. Risks were highest with recurrent preterm pregnancies, and for women who delivered only one child, especially if that delivery was preterm.
  
  
  CONCLUSIONS
  Women who deliver spontaneously before 37 weeks had a 2-fold increased risk of CVD mortality compared with women who had delivered after 38 weeks. Even women with spontaneous deliveries at early term (37-38 weeks) had a 41% elevated risk of CVD death compared with women delivering at 39-41 weeks.
authors.affiliation: Connors Center for Women's Health and Gender Biology, Brigham and Women's Hospital, and Department of Medicine, Harvard Medical School, and Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA. Electronic address: jr33@partners.org.
authors.forename: Janet W
authors.initials: JW
authors.lastname: Rich-Edwards
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, and Medical Birth Registry of Norway, Norwegian Institute of Public Health, Bergen, Norway.
authors.forename: Kari
authors.initials: K
authors.lastname: Klungsoyr
authors.affiliation: National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC.
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Wilcox
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, and Medical Birth Registry of Norway, Norwegian Institute of Public Health, Bergen, Norway.
authors.forename: Rolv
authors.initials: R
authors.lastname: Skjaerven
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000401:mortality; D002423:Cause of Death; D003327:Coronary Disease / Q000401:mortality*; D005260:Female; D005865:Gestational Age; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D010298:Parity; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D020521:Stroke / Q000401:mortality*; D047929:Term Birth; D013997:Time Factors; D055815:Young Adult
keywords: cardiovascular diseases; epidemiology; pregnancy; prevention; risk factors