Estrogen administration enhances thrombin generation in rats.

Venous thrombosis is a serious disorder that may be fatal if complicated by pulmonary embolism. Venous thrombosis is usually related to one of three factors: reduced blood flow, changes in vessel wall integrity, or changes in the blood composition. Factors leading to thrombosis are classified as either genetic or acquired. Puerperium and oral contraceptives are examples of the acquired factors. The risk of thrombosis during pregnancy is high compared to that in the overall population,. however, this increases by three to five times in puerperium. Deep vein thrombosis (DVT) complicated by pulmonary thromboembolism (PE) is considered the leading cause of maternal death in the United States and Europe [Am. J. Obstet. Gynecol. 164 (1991) 603; Obstet. Gynecol. 84 (1994) 240] and the third cause in Japan [M Ishikawa, Maternal mortality and pulmonary thromboembolism. Study on maternal mortality in Japan. Report from the Ministry of Health of Japan in Maternal and Child Health Research, 1996. p. 123-128]. Patients without history of familial thrombophilia have 14-fold higher risk of DVT during puerperium [Thromb. Haemost. 25 (1999) 610]. Little is known about the underlying mechanism of thrombotic disorders in puerperium. It is recognized that oral contraceptive estrogen enhances the risk of DVT [Am. J. Epidemiol. 133 (1991) 32]. However, there is little research regarding the relation between estrogen and blood coagulation, although it is known that plasma estrogen reaches extremely high levels near term. We assume that high-level plasma estrogen plays an important role in the blood coagulation activity that results in the occurrence of DVT. To assess this likely association, we studied the effects of high estrogen levels on coagulation in rat plasma.