This is typically a symptom of the disorder when severe blood loss occurs.Other reported symptoms that are related to the condition:   

Prolonged periods of bleeding due to surgery, injury, or post birth. Melena - Associated with acute gastrointestinal bleeding, dark black, tarry feces. Hematochezia - Lower gastrointestinal bleeding, passage of fresh, bright red blood through the anus secreted in or with stools. If associated with upper gastrointestinal bleeding, suggestive of a more life-threatening issue.Type I: Severe hemorrhages are indicators of a more severe prothrombin deficiency that account for muscle hematomas, intracranial bleeding, postoperative bleeding, and umbilical cord hemorrhage, which may also occur depending on the severity, respectively. Type II: Symptoms are usually more capricious, but can include a variety of the symptoms described previously. Less severe cases of the disorder typically do not involve spontaneous bleeding. Causes
Hypoprothrombinemia can be the result of a genetic defect, may be acquired as the result of another disease process, or may be an adverse effect of medication. For example, 5-10% of patients with systemic lupus erythematosus exhibit acquired hypoprothrombinemia due to the presence of autoantibodies which bind to prothrombin and remove it from the bloodstream (lupus anticoagulant-hypoprothrombinemia syndrome). The most common viral pathogen that is involved is Adenovirus, with a prevalence of 50% in postviral cases. Inheritance
Autosomal recessive condition in which both parents must carry the recessive gene in order to pass the disease on to offspring. If both parents have the autosomal recessive condition, the chance of mutation in offspring increases to 100%.
Anticoagulants: warfarin overdose: Used as a treatment for prevention of blood clots, however, like most drugs, side effects have been shown to increase risk of excessive bleeding by functioning in the disruption of hepatic synthesis of coagulation factors II, VII, IX, and X. Vitamin K is an antagonist to warfarin drug, reversing its activity, causing it to be less effective in the process of blood clotting. Warfarin intake has been shown to interfere with Vitamin-K metabolism. Diagnosis
Diagnosis of inherited hypoprothrombinemia, relies heavily on a patients medical history, family history of bleeding issues, and lab exams performed by a hematologist. A physical examination by a general physician should also be performed in order to determine whether the condition is congenital or acquired, as well as ruling out other possible conditions with similar symptoms. For acquired forms, information must be taken regarding current diseases and medications taken by the patient, if applicable.Lab tests that are performed to determine diagnosis:

Factor assays: To observe the performance of specific factors (II) to identify missing/poorly performing factors. These lab tests are typically performed first in order to determine the status of the factor. Prothrombin blood test: Determines if patient has deficient or low levels of Factor II. Vitamin K1 test: Performed to evaluate bleeding of unknown causes, nosebleeds, and identified bruising. To accomplish this, a band is wrapped around the patients arm, 4 inches above the superficial vein site in the elbow pit. The vein is penetrated with the needle and amount of blood required for testing is obtained.