This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Physiological changes during Pregnancy, Subject name: Gynaecology & Obstetrics
[{'content': 'Which of the following decreases during pregnancy? \nSelect and explain. \nA. Systemic venous resistance, B. CO, C. HR, D. Plasma volume', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Systemic venous resistanceChanges during pregnancy:* Increased in cardiac output* Increase in HR* Increase in plasma volume* Decrease in SVR by (-21%) due to smooth muscle relaxing effect of progesterone, NO, prostaglandins or ANP.* In spite of the large increase in cardiac output, the maternal BP (BP=COxSVR) is decreased due to decrease in SVR. There is overall decrease in diastolic blood pressure (BP) and mean arterial pressure (MAP) by 5-10mmHg', 'role': 'assistant'}]