Systemic changes in haemostatic balance are not associated with increased levels of circulating microparticles in women with recurrent spontaneous abortion

PROBLEM: Placental fibrin deposits in patients wih recurrent spontaneous abortion (RSA) indicate an exaggerated haemostatic response. This 'hypercoagulability' may involve pro-coagulant factors such as circulating microparticles (MPs). We investigated the relationship between circulating pro-coagulant MPs and systemic coagulation in RSA patients. METHOD OF STUDY: Platelet- and endothelial cell-derived microparticles (PMPs, EMPs) were evaluated by flow cytometry in RSA patients (n = 51) and compared to controls (n = 24) using annexin V (total numbers of MP), and antibodies against CD61, CD63 and CD62P (PMP), as well as CD144 and CD62E (EMP). Prothrombin fragment 1 + 2 (F(1+2)) and thrombin generation were determined to assess the pro-coagulant potential of MP. RESULTS: Numbers of annexin V-binding MP were nearly similar in RSA patients and controls. However, a subgroup of ten RSA patients (10/51; 20%) presented with MP concentrations >10,000 x 10(6)/L, compared to only one women out of the control group (1/24; 4%; P = 0.038). Neither PMP and EMP nor F(1+2) and thrombin generation differed significantly within the study population. CONCLUSION: The present study shows that circulating MPs are not directly associated with the extent of systemic coagulation activation in RSA patients. We hypothesize that increased numbers of circulating MPs either are only indirectly associated with coagulation during pregnancy of RSA patients, or affect abortion via mechanisms independently from hypercoagulation.