A prospective study investigating the mechanism of thrombocytopenia in preeclampsia.

Hemostatic and platelet function studies were performed prospectively on 61 preeclamptic patients and 24 healthy pregnant control patients to delineate possible causes of thrombocytopenia in preeclampsia. Thrombocytopenia occurred in 50% of the preeclamptic patients, and was accompanied by qualitative platelet defects as shown by an increased bleeding time and decreased biosynthesis of thromboxane A2. All patients had normal routine coagulation and protamine sulphate paracoagulation assays. All nulliparous patients had normal levels of fibrinopeptide A, but approximately 60% of parous patients had slight elevations of fibrinopeptide A. Elevated levels of platelet-associated immunoglobulin G (IgG) were demonstrated in 35% of all preeclamptic patients and were inversely correlated (r = -0.524) with the severity of the thrombocytopenia. This study indicates that, at least in nulliparous patients, thrombin action is not a major contributor to the development of thrombocytopenia in preeclampsia. The observation of elevated levels of platelet-associated IgG suggests that immune mechanisms could contribute to the thrombocytopenia in some patients.