We sought to validate several clinical risk factors previously described for preeclampsia in a large contemporary multicenter prospective cohort.We enrolled women from three sites before 15 weeks of gestation. Demographic and clinical risk factors were collected through standardized chart review. The main outcome of preeclampsia was diagnosed using the American College of Obstetricians and Gynecologists definitions from 2002. Multivariable logistic regression was used to control for confounders.Two thousand six hundred thirty-seven women are included in this analysis; 237 (9.0%) developed preeclampsia. In adjusted analysis, chronic hypertension (adjusted odds ratio [OR] 2.72; 95% confidence interval 1.78-4.13), pregestational diabetes (adjusted OR 3.88; 2.08-7.26), multiple gestation (adjusted OR 2.96; 1.74-5.03), African American race (adjusted OR 1.91; 1.35-2.71), prior preeclampsia (adjusted OR 3.63; 2.29-5.73), nulliparity (adjusted OR 1.73; 1.26-2.38), assisted reproductive techniques (adjusted OR: 1.72; 1.10-2.68), and being overweight (adjusted OR for body mass index [BMI, kg/m] greater than 25-30: 1.65; 1.13-2.41) or obese (adjusted OR for BMI greater than 30-35: 2.34, 1.51-3.61; adjusted OR for BMI greater than 35-40: 3.59, 2.13-6.03; adjusted OR for BMI greater than 40: 6.04, 3.56-10.24) were associated with preeclampsia, but advanced maternal age was not. Similar associations were found for severe preeclampsia. A dose-response effect was observed in the relationship between BMI and both preeclampsia and severe preeclampsia. Being overweight or obese was the most important risk factor for both preeclampsia and severe preeclampsia with an attributable risk percent of 64.9% and 64.4%, respectively.In this contemporary cohort, increasingly prevalent and potentially modifiable factors were confirmed as significant risk factors for preeclampsia and severe preeclampsia, the most important being overweight or obese. This information is important to guide public health efforts in preeclampsia prevention.: II.