Changes in Platelet Activation Associated with Hypertensive Disorders of Pregnancy.

Abstract 3504

Poster Board III-441

Pre-eclampsia is associated with increased rates of platelet clearance, changes in platelet function, and platelet activation. The goal of the current study was to assess changes in basal levels of platelet activation in individuals with pregnancies with hypertensive complications, and to compare those levels to individuals with uncomplicated pregnancies. In this study, three indices of platelet activation, platelet CD63 expression (% CD63), monocyte/platelet aggregate (% MP) formation, and neutrophil/platelet aggregate formation (% GP) were measured in whole blood by flow cytometry using specific, fluorescently-labeled monoclonal antibodies in 20 nulliparous women of reproductive age who subsequently conceived singleton pregnancies. Subjects were re-examined in early (11 - 16 wks) and late pregnancy (31 - 34 wks), as well as ∼15 months postpartum. Three of these women were diagnosed with hypertensive complications (1 gestational hypertension with intrauterine growth restriction, 2 pre-eclampsia), and delivered at term. However, all subjects were normotensive at all study points. The data are expressed as the mean ± SEM. P < 0.05 is considered significant. Subjects with uncomplicated pregnancies were 29.4 ± 0.77 years old with a BMI of 23.6 ± 0.83 kg/m² at the time of the pre-pregnancy studies. Subjects with pregnancies with hypertensive complications were 32.0 ± 1.5 years old with a BMI of 21.3 ± 0.88 kg/m² at the time of the pre-pregnancy studies. No differences in the platelet activation markers, % CD63 and % GP, were observed in this study. In contrast, a strong trend for increased % MP formation in pre-pregnancy measurements in those women destined to develop hypertensive complications of pregnancy was observed (p=0.062): Women with pregnancies with hypertensive complications had substantially more % MP formation (20.9 ± 10.3%) than women with uncomplicated pregnancies (7.1 ± 4.2%). In individuals with uncomplicated pregnancies, an increase in the % MP formation over pregnancy was observed over time, and this platelet activation marker remains elevated (20.2 ± 4.4%, p=0.015) in postpartum measurements when compared to pre-pregnancy values. A markedly different pattern was observed in women with pregnancies with hypertensive complications with postpartum values below the pre-pregnancy values (5.3 ± 12.2% vs. 20.9 ± 10.3%). These combined observations suggest that hypertensive complications of pregnancy are associated with alterations in the pattern of platelet activation in pregnancy and postpartum.