Platelet Aggregation in Vitro and Ex Vivo in Normal Pregnancy, Pregnancy-Induced Hypertension, and Preeclampsia

Abstract

Objective: To compare women with preeclampsia, pregnancy-induced hypertension (PIH), and norrnotensive pregnant women with regard to different coagulation variables including filtragometry, reflecting the in vivo situation more closely than conventional in vitro methods.

Methods: Blood was sampled for analyses of platelet count, antithrombin III (AT III) concentration, activated partial thromboplastin (APT) time, and prothrombin time in 15 patients with preeclampsia, 11 with PIH, and 13 normotensive pregnant women in the third trimester. We also applied whole blood aggregometry in vitro by the addition of 1 μg of collagen to 1 mL of diluted blood and filtragometry measuring spontaneous platelet aggregation ex vivo by estimating the time to develop a pressure gradient of 10 mm Hg over a filter occluded by platelet aggregates. The Kruskal—Wallis nonparametric test was used for statistical analyses.

Results: APT time and prothrombin time did not differ among the three groups. Platelet count was normal except for a slight reduction in two patients in the preeclampsia group. AT III was lower in preeclampsia than in PIH and normotensive pregnancy; P < 0.05. Aggregation after the addition of collagen was approximately 50% lower in the preeclampsia group compared with the PIH and normotensive groups (P < 0.01). Filter occlusion time (seconds) during filtragometry was similar in preeclampsia (median 65; range 23–768) and PIH (median 87; range 12–739) and shorter than in the normal pregnancy (median 494; range 74–754), and P < 0.05.

Conclusions: Preeclampsia but not PIH is asSociated with reduced platelet aggregation in vitro, possibly reflecting the exhaustion of platelets. The results from filtragometry, most resembling the in vivo situation, however, implies an enhanced aggregation both in preeclampsia and PIH.

Key Words:

• Pregnancy hypertension
• Platelet aggregation
• Filtragometry