ObjectiveTo determine the site of origin of increased concentrations of plasma endothelin-1 in patients with severe preeclampsia.MethodsTwelve patients with severe preeclampsia undergoing an indicated abdominal delivery had endothelin-1 levels measured from plasma specimens drawn from right and left uterine and antecubital veins before delivery and after placenta removal with uterine curettage. Twelve uncomplicated control patients undergoing abdominal delivery had endothelin-1 concentrations drawn by an identical protocol. Clinical staff members were blinded to endothelin-1 results and laboratory staff were blinded to patient group assignment and sample source. Endothelin-1 plasma concentrations were determined by radioimmunoassay and data were analyzed by pairedttest.ResultsNo difference in endothelin-1 concentration was noted with respect to placental location, central versus peripheral, or predelivery versus postdelivery sampling procedures. Overall, patients with preeclampsia had higher plasma concentrations of endothelin-1 (mean 11.0 ± 6.6 pg/mL) compared with normotensive patients (mean 8.4 ± 46.7 pg/mL,P< .005).ConclusionThe decidual-placental interface does not appear to be the source of increased plasma endothelin-1 concentrations found in severe preeclampsia. The origin of this increase remains uncertain.