Causes. Hematomas are always the result of some type of trauma caused by anything from a critical car accident or serious fall to a minor cough or sneeze. Trauma results in the walls of a blood vessel becoming compromised and then leaking out of the circulatory system becoming stagnant. Some types of medications such as anticoagulants may increase the risk of developing hematomas. Hematomas can also be the result of a clotting disorder where the platelets do not function normally or where there are fewer platelets then there should be in the blood. Injuries to the nose and/or ear may also easily result in hematomas. Hematomas are also heavily associated with bone breaks and fractures. Hematomas may also occur more often during pregnancy due to the increased volume of blood.