How does oxygen consumption change during pregnancy?

How does oxygen consumption change during pregnancy?

• A. Decreases 10-20 percent
• B. Increases 20-40 percent by term
• C. Increases 60-80 percent
• D. Stays the same

Answer: (B)

During pregnancy the body's oxygen needs rise because both the fetus and the placenta are growing, and maternal tissues expand to support that growth. To meet these higher demands, oxygen consumption increases by about 20–40 percent by term. This increase comes from several physiologic changes: the maternal metabolic rate climbs, cardiac output and blood volume rise to deliver more oxygen to tissues, and the lungs become more ventilated (driven by progesterone) to bring in more oxygen, even though CO2 levels fall due to increased ventilation. The placenta and fetus also consume oxygen, contributing to the overall rise in maternal oxygen use. So the best choice reflects a moderate increase rather than a decrease, no change, or an exaggerated rise. The increase is around 20–40 percent by term.

During pregnancy the body's oxygen needs rise because both the fetus and the placenta are growing, and maternal tissues expand to support that growth. To meet these higher demands, oxygen consumption increases by about 20–40 percent by term.

This increase comes from several physiologic changes: the maternal metabolic rate climbs, cardiac output and blood volume rise to deliver more oxygen to tissues, and the lungs become more ventilated (driven by progesterone) to bring in more oxygen, even though CO2 levels fall due to increased ventilation. The placenta and fetus also consume oxygen, contributing to the overall rise in maternal oxygen use.

So the best choice reflects a moderate increase rather than a decrease, no change, or an exaggerated rise. The increase is around 20–40 percent by term.