Minute ventilation changes during pregnancy by term?

Minute ventilation changes during pregnancy by term?

• A. Decreases 30 to 50%
• B. Increases 15 to 25%
• C. Increases 30 to 50%
• D. Remains unchanged

Answer: (C)

During pregnancy the respiratory system adapts to support both mother and fetus, and the key change is a substantial boost in minute ventilation by term. This rise is driven primarily by increased tidal volume due to progesterone’s stimulation of the respiratory centers, which makes the mother more sensitive to CO2. As a result, breaths become deeper, and the overall ventilation (tidal volume times respiratory rate) climbs by about 30–50%. This ventilatory boost helps meet higher metabolic demands and enhances gas exchange, lowering arterial CO2 levels. The body also undergoes a mild respiratory alkalosis as a result, and the kidneys compensate over time by excreting bicarbonate to keep the pH closer to normal. Diaphragmatic elevation and reduced lung volumes can make breathlessness more noticeable, but the total ventilation continues to increase. So the correct idea is that minute ventilation increases significantly—roughly 30 to 50%—by term.

During pregnancy the respiratory system adapts to support both mother and fetus, and the key change is a substantial boost in minute ventilation by term. This rise is driven primarily by increased tidal volume due to progesterone’s stimulation of the respiratory centers, which makes the mother more sensitive to CO2. As a result, breaths become deeper, and the overall ventilation (tidal volume times respiratory rate) climbs by about 30–50%.

This ventilatory boost helps meet higher metabolic demands and enhances gas exchange, lowering arterial CO2 levels. The body also undergoes a mild respiratory alkalosis as a result, and the kidneys compensate over time by excreting bicarbonate to keep the pH closer to normal. Diaphragmatic elevation and reduced lung volumes can make breathlessness more noticeable, but the total ventilation continues to increase.

So the correct idea is that minute ventilation increases significantly—roughly 30 to 50%—by term.