This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Platelet & Coagulation disorders, Subject name: Medicine
[{'content': 'Which of these is a feature of hemorrhagic disease of new born? \nSelect and explain. \nA. Prolonged prothrombin time, B. Defective platelet count, C. Prolonged bleeding time, D. Prolonged thrombin time', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Normal newborns are moderately deficient in vitamin K. This deficiency increases on 3rd to 5th day when, vitamin K level falls fuher. The serum level of vitamin K stas increasing from 13th to 15th day of life and achieves adult level at 3 months. In hemorrhagic disease of the newborn, there is delay in achieving the normal vitamin K level. Prolongation of PT values is the most common and earliest finding in vitamin K-deficient patients due to reduction in prothrombin, factor VII, IX, and X levels. F VII has the shoest half-life among these factors that can prolong the PT before changes in the aPTT.', 'role': 'assistant'}]