Familial Risk of Preeclampsia in Newfoundland: A Population-Based Study

ABSTRACT. This study sought to quantify the familial risk of preeclampsia (proteinuric hypertension) in Newfoundland and to identify characteristics in probands that predict increased familial risk. Reviewed were 5173 obstetric charts from 10 hospitals, representing 99% of deliveries on the island of Newfoundland for a 1-yr period from April 1996 to March 1997; pregnancy-induced hypertension was diagnosed according to strict criteria. Family obstetric histories were obtained from identified probands with preeclampsia, and sisters and mothers of probands were interviewed. In addition, the obstetric charts from sisters and mothers were reviewed to identify preeclampsia. The incidence of preeclampsia in the population was 5.6% ( n = 292), and in primiparous women it was 7.9%. Factors independently associated with increased risk of preeclampsia included primiparous delivery, multiple gestation, pregestational and gestational diabetes, maternal age of more than 35 yr, and region of the province. Of 330 sisters identified, 217 had 445 pregnancies, with 331 charts located for review. The incidence of preeclampsia (based on chart review) in 163 primiparous sisters was 20.2%. The relative risk of preeclampsia in primiparous sisters of probands with preeclampsia compared with primiparous women in the population was 2.6 (95% confidence interval, 1.8 to 3.6). Factors in probands independently associated with a higher risk of preeclampsia in sisters included at least 2+ proteinuria and region of the province. This population-based study, which used unbiased ascertainment and strict diagnostic criteria, demonstrated a significantly higher risk of preeclampsia in sisters of probands with preeclampsia, particularly when probands were defined by severity of preeclampsia and by geographic region.