title: Interpregnancy change in smoking habits and risk of preeclampsia: a population-based study.
abstract: BACKGROUND
  Maternal smoking has been associated with decreased risk of preeclampsia; however, it is uncertain whether this association is causal. An argument for causality would be strengthened if changes in smoking status across consecutive pregnancies were related to the risk of preeclampsia.
  
  
  METHODS
  We used data from the National Swedish Birth Register to ascertain the associations between changes in smoking status during the first two successive pregnancies and risk of preeclampsia in the second pregnancy in 371,627 women between 1992 and 2006. Multivariable logistic regression models were used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI).
  
  
  RESULTS
  Compared to women who did not smoke in either pregnancy, the risk of preeclampsia was reduced in women who smoked in both pregnancies (adjusted OR = 0.54; 95% CI = 0.47, 0.63), in those who only smoked in second pregnancy (OR = 0.76; 95% CI = 0.58, 0.99) and, to a lesser extent, in women who smoked only in the first pregnancy (OR = 0.81; 95% CI = 0.70, 0.94). History of preeclampsia in the first pregnancy did not substantially modify these associations.
  
  
  CONCLUSIONS
  These data add support to a causal interpretation of the observed inverse association between smoking during pregnancy and risk of preeclampsia.
authors: Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine University of Michigan, Ann Arbor, Michigan, USA.
authors: Uma C
authors: UC
authors: Perni
authors: Anna-Karin
authors: AK
authors: Wikström
authors: Sven
authors: S
authors: Cnattingius
authors: Eduardo
authors: E
authors: Villamor
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D016015:Logistic Models; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D013548:Sweden / Q000453:epidemiology