title: Risk of pre-eclampsia in first and subsequent pregnancies: prospective cohort study.
abstract: OBJECTIVE
  To investigate whether pre-eclampsia is more common in first pregnancies solely because fewer affected women, who presumably have a higher risk of recurrence, go on to have subsequent pregnancies.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Swedish Medical Birth Register.
  
  
  METHODS
  763 795 primiparous mothers who had their first births in Sweden, 1987-2004.
  
  
  METHODS
  Pre-eclampsia.
  
  
  RESULTS
  The risk of pre-eclampsia was 4.1% in the first pregnancy and 1.7% in later pregnancies overall. However, the risk was 14.7% in the second pregnancy for women who had had pre-eclampsia in their first pregnancy and 31.9% for women who had had pre-eclampsia in the previous two pregnancies. The risk for multiparous women without a history of pre-eclampsia was around 1%. The incidence of pre-eclampsia associated with delivery before 34 weeks' gestation was 0.42% in primiparous women, 0.11% in multiparous women without a history of pre-eclampsia, and 6.8% and 12.5% in women who had had one or two previous pregnancies affected, respectively. The proportion of women who went on to have a further pregnancy was 4-5% lower after having a pregnancy with any pre-eclampsia but over 10% lower if pre-eclampsia was associated with very preterm delivery. The estimated risk of pre-eclampsia in parous women did not change with standardisation for pregnancy rates.
  
  
  CONCLUSIONS
  Having pre-eclampsia in one pregnancy is a poor predictor of subsequent pregnancy but a strong predictor for recurrence of pre-eclampsia in future gestations. The lower overall risk of pre-eclampsia among parous women was not explained by fewer conceptions among women who had had pre-eclampsia in a previous gestation. Early onset pre-eclampsia might be associated with a reduced likelihood of a future pregnancy and with more recurrences than late onset pre-eclampsia when there are further pregnancies. Findings are consistent with the existence of two distinct conditions: a severe recurrent early onset type affected by chronic factors, genetic or environmental, and a milder sporadic form affected by transient factors.
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, 677 Huntington Ave, Boston, MA 02115, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Hernández-Díaz
authors.forename: Sengwee
authors.initials: S
authors.lastname: Toh
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D010298:Parity; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology