Decreasing Platelet Aggregation Despite Increasing Soluble P-selectin during Pregnancy in Women with and without Heterozygous Factor V Leiden Mutation.

Risk of venous thromboembolism (VTE) is increased in pregnancy and postpartum, and 40% of VTEs in pregnancy (Caucasians) are associated with heterozygous factor V Leiden mutation (FVL). Thrombin generation is increased in individuals with FVL and in pregnant women, and thrombin amplifies both platelet and coagulation activation. Although both contribute to VTE pathophysiology, the mechanisms of platelet activation in pregnant women, particularly with heterozygous FVL, remain poorly understood.To describe the physiological course of the platelet activation marker plasma soluble P-selectin (sP-selectin), whole blood platelet aggregation, and thromboelastography (TEG) parameters throughout pregnancy and postpartum, and assess differences between women with and without heterozygous FVL.A total of 22 pregnant women with heterozygous FVL and 22 without were enrolled. Blood samples were collected at multiple time points during and after pregnancy. Platelet activation and aggregation were evaluated using sP-selectin, multiple electrode aggregometry (MEA) with adenosine diphosphate, arachidonic acid, thrombin receptor-activating peptide-6 as agonists, and TEG.sP-selectin levels increased significantly during pregnancy, while platelet aggregation decreased in response to all agonists (<i>P</i> < 0.005). TEG maximum amplitude (MA) increased throughout pregnancy. No significant differences were observed between women with and without FVL.In late pregnancy, decreased platelet aggregation responses were observed alongside increased sP-selectin levels, with no differences in levels between women with and without heterozygous FVL. These findings indicate that the presence of heterozygous FVL does not significantly influence platelet function during pregnancy. The cause of the unexpected, reduced platelet aggregation remains unclear and warrants further investigation.