title: History of abortion, preterm and term birth, and risk of gestational hypertension: a population-based study.
abstract: OBJECTIVE
  To examine the consequence of prior abortion and preterm and term birth on the occurrence of gestational hypertension in the subsequent pregnancy.
  
  
  METHODS
  A population-based, retrospective, cohort study was conducted based on 140,773 pregnancies delivered between 1993 and 1999 in 49 hospitals in northern and central Alberta, Canada. Multivariate logistic regression was applied to estimate ORs with 95% CIs, adjustedfor confounding variables.
  
  
  RESULTS
  The incidence of gestational hypertension was markedly lower in women who previously delivered at term than in primigravid women (2.4% vs. 5.6%) (adjusted OR [aOR]: .41 [.38-.44], p < 0.001). The incidence of gestational hypertension in women with previous preterm birth but without prior abortion or term pregnancy was also lower than in primiparous women (3.9% vs. 5.6%) (aOR: .72 [.54-.95], p<0.05). Moreover, there was a trend toward a decreased incidence of gestational hypertension among women with a longer duration of previous preterm gestation. Although there was a statistically significant decreased incidence of gestational hypertension in pregnancies in women with a previous history of abortion (4.9%) as compared to women without such a history (5.6%) (aOR:.85[95% CI: .77-.93], p < 0.05), 2, 3 or more abortions were not associated with a decreased risk of gestational hypertension, calling into question the clinical significance of the effect of abortion.
  
  
  CONCLUSIONS
  There was a trend toward a decreased incidence of gestational hypertension among women with a longer duration of previous gestation. However, a history of term pregnancy (> or =37 weeks) conveyed the most substantial protection against gestational hypertension in the subsequent pregnancy.
authors.affiliation: Departments of Obstetrics and Gynecology, University of Montreal, Quebec, Canada. xxiong@tulane.edu
authors.forename: Xu
authors.initials: X
authors.lastname: Xiong
authors.forename: William D
authors.initials: WD
authors.lastname: Fraser
authors.forename: Nestor N
authors.initials: NN
authors.lastname: Demianczuk
mesh_terms: D000028:Abortion, Induced / Q000009:adverse effects*; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D008487:Medical History Taking; D016017:Odds Ratio; D011247:Pregnancy; D047928:Premature Birth; D012189:Retrospective Studies; D012307:Risk Factors