Risk factors associated with preeclampsia in healthy nulliparous women

OBJECTIVE: Our goal was to identify risk factors for the development of preeclampsia in nulliparous women enrolled in a multicenter trial comparing calcium supplementation to a placebo. STUDY DESIGN: A total of 4589 women from five centers was studied. Analysis of risk factors for preeclampsia was performed in 4314 who carried the pregnancy to >20 weeks. Baseline systolic and diastolic blood pressure, demographic characteristics, and findings after randomization were examined for the prediction of preeclampsia. Preeclampsia was defined as hypertension (diastolic blood pressure greater than or equal to 90 mm Hg on two occasions 4 hours to 1 week apart) and proteinuria (greater than or equal to 3C0 mg/24 hours, a protein/creatinine ratio greater than or equal to 0.35, one dipstick measurement greater than or equal to 2+ or two dipstick measurements greater than or equal to 1+ at an interval as specified for diastolic blood pressure). RESULTS: Preeclampsia developed in 326 women (7.6%). The first analysis treated each risk factor as a categoric variable in a univariate regression. Maternal age, blood group and Rh factor, alcohol use, previous abortion or miscarriage, private insurance, and calcium supplementation were not statistically significant. Risk factors initially found to be significant were body mass index, systolic blood pressure, diastolic blood pressure, non-white race (African-American and other), clinical center, and smoking. Adjusted odds ratios computed with a logistic regression model revealed that body mass index (odds ratio 3.22 for greater than or equal to 35 kg/m(2) vs <19.8 kg/m(2)), systolic blood pressure (odds ratic 2.66 for greater than or equal to 120 vs <101 mm Hg), diastolic blood pressure (odds ratio 1.72 for greater than or equal to 61 mm Hg vs <60 mm Hg), and clinical center (odds ratio 1.85 for Memphis vs the other clinical centers) were statistically significant predictors of preeclampsia. Results of the final model fit revealed that preeclampsia risk increases significantly (p < 0.0001) with increased body mass index at randomization, as well as with increased systolic and diastolic blood pressure at randomization. Calcium supplementation had no effect on the risks posed by body mass index and blood pressure. Among risk factors developing after randomization, an abnormal result of a glucose screen (plasma glucose greater than or equal to 140 mg/dl 1 hour after a 50 gm glucose challenge) was not found to be associated with a significant risk of preeclampsia. CONCLUSION: These risk factors should be of value in counseling women regarding preeclampsia and should aid in understanding the pathophysiologic characteristics of this syndrome.