Prediction of maternal predisposition to preeclampsia

Objective: To derive a prediction index based on the most salient patient history, laboratory, and clinical parameters for identifying women at high risk for developing preeclampsia (PE). Methods: Nonpregnant women with a history of PE (n = 101) were compared with nonpregnant parous women with a history of one or more successful normotensive pregnancies (n = 50) but with comparable age, gestation, and parity profiles. The parameters included a medical examination (demographics, patient history, family history, and clinical and obstetrical findings), laboratory investigations (hemostasis, coagulation, and vitamins), and morphological and functional tests (cardiovascular and renal functions). Stepwise logistic regression analysis was applied to develop a three-step PE prediction index based on the most discriminant parameters. Results: Patients with and without PE differed significantly (p < 0.05) with respect to 1) maternal history of chronic hypertension, body mass index, and blood pressure; 2) APTT, PT, activated factor VIII, homocystein, free protein S and vitamin B1; and 3) relative plasma volume. Based on these three sets of parameters, a three-step PE prediction index was developed. The likelihood ratio of a positive index score was equal to 3.4, 7.3, and 8.8, respectively. Thus, assuming a PE prevalence (or prior probability) of 5%, a patient's chances of developing PE when presenting with a positive score on the three-step prediction index were 15%, 28%, and 32%, respectively. Discussion: In the absence of welldefined pre-pregnancy screening guidelines for PE, the present study attempts to proceed in a stepwise fashion by looking at medical examination data first, requesting, if necessary, specific hemostasis and coagulation tests next, and finally measuring the relative plasma volume for confirmatory purposes. This approach offers a satisfactory positive predictive value and cost efficiency ratio.