Platelet activation in the hypertensive disorders of pregnancy

OBJECTIVE: The purpose of this study was to determine whether platelet activation occurs only in preeclampsia or also in normal pregnancy. STUDY DESIGN: Thirty women with preeclampsia, 30 women with gestational hypertension, 20 women with essential hypertension, 30 pregnant women with normotension, and 30 nonpregnant women were recruited at St George Hospital, Sydney, Australia. Platelet activation was determined by flow cytometry on whole blood samples. RESULTS: Platelet activation was similar in all groups, except the group with preeclampsia. Compared with normal pregnant women, women with preeclampsia had significantly greater CD62 expression (1.35% vs 0.61%; P =.002), CD63 expression (1.73% vs 0.95%; P <.0001) and annexin V binding (1.03% vs 0.66%; P =.03) and significantly fewer circulating platelet microparticles (33 vs 49 x 10(9)/L; P =.001). This was unrelated to other parameters that included platelet counts. Women with gestational hypertension in whom preeclampsia developed did not have enhanced platelet activation profiles. CONCLUSION: Platelet activation is increased in preeclampsia but not in other hypertensive disorders or in normal pregnancy. This may be part of the pathophysiologic factors of preeclampsia complications but is not predictable by the platelet count and is not apparent in all women with preeclampsia.