Total lung volume during pregnancy does what?

• A. Increases
• B. Decreases
• C. Remains unchanged
• D. Varies with activity

Answer: (B)

When a woman is pregnant, the uterus grows and pushes the diaphragm upward, shrinking the vertical space inside the chest. That anatomical change reduces the lungs’ capacity to hold air after a normal exhale (functional residual capacity) and lowers expiratory reserve volume. Although breathing becomes deeper and faster because progesterone raises the respiratory drive (tidal volume increases), this does not fully compensate for the reduced thoracic space. The net result is a modest decrease in total lung capacity. This change is primarily due to mechanical and hormonal effects of pregnancy rather than activity level, so total lung volume tends to go down as pregnancy progresses.