<s>[INST] context: According to the given scenario and clinical presentation, most likely the patient is having physiological dyspnea of pregnancy which is quite common. In case of Pulmonary embolism, there is chest pain associated with dyspnea and hemoptysis and is a more acute event associated with desaturation. Asthmatic patient will usually have a past history, chest findings of wheezing and decreased oxygen saturation Left hea failure presents with dyspnea of varying severity, B/L basal crepts Physiological dyspnea It occurs in 60% to 70% of normal pregnant women by 30 weeks of gestation, but can occur as early as at the end of first trimester. There is decrease in FRC (Functional Residual Capacity) mores significantly by 6th month Total lung capacity is unchanged Tidal volume and minute ventilation increase significantly as pregnancy advances. Increase in minute ventilation is secondary to stimulatory effect of progesterone to increase respiratory drive Due to increase in minute ventilation during pregnancy, it may make the patient feel as if they are hyperventilating and contribute to the feeling of shoness of breath/dyspnea Reassurance is enough and no medical intervention is needed. [/INST] question: A 31 year old woman in 2nd trimester of her pregnancy, has come to OPD with a complaint of dyspnea on exeion. There is no history of chest pain, cough or fever and the patient has no known cardiac disease .On physical examination examination, her pulse is 75 / min, BP is 110/70, and Sp02 is 96% . Chest and CVS examination is unremarkable. What could be the most probable cause of this patient's clinical presentation? | options: A: Asthma B: Pulmonary embolism C: Physiological dyspnea of pregnancy D: Left hea failure | answer: C </s>