Prostacyclin/thromboxane early changes in pregnancies that are complicated by preeclampsia

Objective: The purpose of this study was to examine 6-keto-prostaglandin F1α and thromboxane B2 plasma levels throughout normotensive and preeclamptic pregnancies and to analyze the predictive values of these quantifications for the detection of preeclampsia during the second trimester of pregnancy. Study Design: Blood samples were collected from 30 healthy, nonpregnant women and at 4-week intervals from a cohort of nulliparous women who were recruited before 16 weeks of gestation. Preeclampsia developed in 26 patients; 52 normotensive control subjects were matched from the same cohort. The 6-keto-prostaglandin F1α and thromboxane B2 were assayed by radioimmunoassay. Trends were compared between pregnancy groups and with the nonpregnant women. Predictive values were determined with the second-trimester assessments. Results: The 6-keto-prostaglandin F1α/thromboxane B2 ratio decreased throughout pregnancy in women with preeclampsia; there were no significant changes in normotensive women. We found higher thromboxane B2 levels within the group with preeclampsia during the first gestational trimester (preeclampsia, 188 ± 17 pg/mL; control, 119 ± 4.8 pg/mL [mean ± SEM]; P = .001). During the third trimester, patients with preeclampsia had lower 6-keto-prostaglandin F1α levels than did control subjects (preeclampsia, 191 ± 9.8 pg/mL; control, 288 ± 10 pg/mL; P = .001). The 6-keto-prostaglandin F1α/thromboxane B2 ratio was suitable to calculate predictive values; the best cutoff point and time interval were 3.0 and 22 to 26 weeks of gestation, respectively. Sensitivity, specificity, and positive and negative predictive values were 88%, 97%, 69%, and 99%, respectively; the odds ratio was 14.6 (95% CI, 6.9-30.4). Conclusion: The prostacyclin/thromboxane ratio favored vasoconstriction early in gestation in women in whom preeclampsia developed. A 6-keto-prostaglandin F1α/thromboxane B2 ratio of ≤3.0 at 22 to 26 weeks of gestation had a high predictive value for the development of preeclampsia.