Comparison of Fibrinolysis in Peripartum and Non-Pregnant Mares Using Modified Thromboelastography

During pregnancy and the peripartum period in women, hypofibrinolysis and hypercoagulation minimize excessive hemorrhage risk during parturition. While hypercoagulation is documented in peripartum mares, hypofibrinolysis is not. This study aimed to characterize and compare the fibrinolytic potential of healthy, non-pregnant mares and peripartum mares using tissue-factor (TF)-activated, tissue-plasminogen-activator (tPA)-modified thromboelastography (TEG). TF-activated TEG modified with tPA (500 and 650 U/mL) was performed on plasma samples from 9 pregnant mares at 3, 2, and 1 month pre-partum and 1, 7, and 30 days post-partum, as well as on time-matched samples from 6 non-pregnant mares. At both tPA concentrations, there were relative increases in clot strength [MA] and changes in lysis parameters consistent with hypofibrinolysis (increased CL30 and decreased Ly30) in the pregnant mares compared to the non-pregnant mares. The differences were most frequently detected 1 month pre-partum and at 1 and 7 days post-partum, providing preliminary evidence suggesting pregnant mares are hypofibrinolytic during late gestation and the early post-partum period. However, our small sample size, the unexpected changes in fibrinolysis in the non-pregnant mares over time, and the inconsistent performance of the assay indicate a need for a larger study after further assay optimization to confirm the results. Further investigations of the tPA-modified TEG assay and fibrinolysis in clinical cases are warranted.