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.