Three conditions are required for the formation of thrombus: first, damage to the vascular endothelium; second, altered blood flow status; and third, increased blood coagulability. All these three aspects are the basic conditions for thrombus formation. Thrombosis is the abnormal coagulation of blood in the flow state due to platelet activation and activation of coagulation factors, damage to the vascular endothelium, and activation of platelets and coagulation factors by exposed collagen fibers under the endothelium, thus initiating the endogenous coagulation system. The slow blood flow state is due to surgical braking, etc. The slow blood flow state can allow platelets to aggregate, thereby creating a thrombus. Increased blood coagulation, which is an increase in platelets and clotting factors in the blood, activates the fibrinolytic system, resulting in a hypercoagulable state of the blood, and is most often seen in postpartum or in patients with major blood loss.