The recurrence risk of severe de novo pre‐eclampsia in singleton pregnancies: a population‐based cohort

Objective  Previous studies have found recurrence risks of severe pre‐eclampsia as high as 40%. Our objective was to determine both the recurrence risk of severe de novo pre‐eclampsia and risk factors associated with it in a contemporaneous population. Study design  Population‐based retrospective cohort study. Population  Women who had two or more singleton liveborn or stillborn hospital deliveries in Ontario, Canada between April 1994 and March 2002 and without a history of chronic hypertension Methods  International Classification of Disease codes were used to identify patients in the Canadian Institute for Health Information Discharge Abstract Database. Main outcome measures  The absolute and adjusted risks of recurrent severe de novo pre‐eclampsia were determined. Results  Between 1 April 1994 and 30 March 2002, there were 185 098 women with two or more singleton deliveries >20 weeks in the province of Ontario, Canada. There were 1954 women who had severe de novo pre‐eclampsia in the index pregnancy, 133 of whom had recurrent severe pre‐eclampsia, for a risk of recurrent severe pre‐eclampsia of 6.8% (95% CI 5.7–7.9%). The risk of recurrent severe de novo pre‐eclampsia was increased in women with pre‐existing renal disease (adjusted OR 17.98, 95% CI 3.50–92.52) and those >35 years of age (adjusted OR 3.79, 95% CI 2.04–7.04, reference 20–25 years). Conclusions  The recurrence risk of severe de novo pre‐eclampsia in our population‐based cohort study (6.8%) is lower than previously published reports in selected populations.