This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'True regarding maternal plasma osmolality during pregnancy \nSelect and explain. \nA. Maternal plasma osmolality decreases early in pregnancy, B. Maternal plasma osmolality increases throughout pregnancy, C. Maternal plasma osmolality does not change during pregnancy, D. Maternal plasma osmolality is affected most by increases in sodium', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Increased water retention in pregnancy is normal physiological change of pregnancy. It is mediated by fall in plasma osmolality induced by resetting osmotic thresholds for thirst and vasopressin secretion.', 'role': 'assistant'}]