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': 'Which of the following is the LEAST likely physiological change in pregnancy? \nSelect and explain. \nA. Increase in intravascular volume, B. Increase in cardiac output, C. Increase in stroke volume, D. Increase in peripheral vascular resistance', 'role': 'user'}, {'content': "Answer: D \nExplanation: Blood volume expansion begins early in the first trimester, increases rapidly in the second trimester, and plateaus at about the 30th week. Cardiac output increases approximately 40% during pregnancy, with maximum values achieved at 20-24 weeks' gestation. Stroke volume increases 25-30% during pregnancy, reaching peak values at 12-24 weeks' gestation. Vascular resistance decreases in the first trimester, reaching a nadir of approximately 34% below nonpregnancy levels by 14 to 0 weeks of gestation with a slight increase toward term. Ref: Flick A.A., Kahn D.A. (2013). Chapter 8. Maternal Physiology during Pregnancy & Fetal & Early Neonatal Physiology. In DeCherney A.H., Nathan L, Laufer N, Roman A.S. (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.", 'role': 'assistant'}]