How is oxygen demand met during pregnancy?

How is oxygen demand met during pregnancy?

• A. Decreased minute volume and cardiac output
• B. Increasing minute volume and cardiac output
• C. Increased only CO2 clearance
• D. Decreased appetite

Answer: (B)

Oxygen demand rises in pregnancy because fetal needs and maternal metabolism increase. The body adapts by boosting both how much air is moved per minute and how much blood the heart pumps. Progesterone drives a higher respiratory drive, so tidal volume and overall minute ventilation go up. At the same time, blood volume expands and heart rate rises, increasing cardiac output. This combination improves oxygen delivery to maternal tissues and the placenta (and thus to the fetus). CO2 clearance also rises with the greater ventilation, but meeting the higher oxygen demand relies on both increased minute volume and increased cardiac output. Options suggesting decreased ventilation or cardiac output, or focusing only on CO2 clearance, do not meet the need.

Oxygen demand rises in pregnancy because fetal needs and maternal metabolism increase. The body adapts by boosting both how much air is moved per minute and how much blood the heart pumps. Progesterone drives a higher respiratory drive, so tidal volume and overall minute ventilation go up. At the same time, blood volume expands and heart rate rises, increasing cardiac output. This combination improves oxygen delivery to maternal tissues and the placenta (and thus to the fetus). CO2 clearance also rises with the greater ventilation, but meeting the higher oxygen demand relies on both increased minute volume and increased cardiac output. Options suggesting decreased ventilation or cardiac output, or focusing only on CO2 clearance, do not meet the need.