Risk factors and clinical manifestations of pre-eclampsia

Objective To study associations between established risk factors for pre-ec lampsia and different clinical manifestations of the disease. Design A population-based, nested case-control study. Setting Information from 12,804 consecutive deliveries that took place over three years at a birth clinic, which alone serves a population of nearly 2 40,000 in Rogaland county, Norway. Subjects Cases of pre-eclampsia (n = 323) and healthy controls (n = 650) we re selected. Pre-eclampsia was defined as increase in diastolic blood press ure (greater than or equal to 25 mmHg to greater than or equal to 90 mmHg) and proteinuria (greater than or equal to 1+ by dipstick testing) after 20 weeks of pregnancy. Main study measures Parity, previous pre-eclampsia, blood pressure, materna l weight, and maternal smoking were included as study variables. Women with pre-eclampsia were grouped according to clinical manifestations of the dis ease (i.e. severity [mild, moderate or severe]) and time of onset (early or late gestation). Associations with the study factors were estimated as rel ative risks (odds ratio, OR). Results Both nulliparity and hypertension increased pre-eclampsia risk, wit h no clear preference for any clinical subtype. High maternal weight was re lated to a higher risk of mild and moderate, but not severe, pre-eclampsia. Previous pre-eclampsia strongly increased the risk for pre-eclampsia in th e current pregnancy, and the risk of early onset disease was especially hig h (OR 42.4; 95% CI 11.9-151.6). Overall, smoking was associated with a redu ced risk for pre-eclampsia (OR 0.6; 95% CI 0.4-0.9). However, no effect of smoking was observed in the early onset disease group and among women with repeated pre-eclampsia. Conclusion Nulliparity and hypertension increased the risk for each subgrou p of pre-eclampsia, but high maternal weight, previous pre-eclampsia and sm oking were not consistently associated with each clinical subtype. This obs ervation may suggest that heterogeneous clinical manifestations of pre-ecla mpsia may be preceded by different pathological mechanisms.