What is the effect of the uterus displacing the diaphragm at term?

At term, the growing uterus exerts upward pressure on the diaphragm, which can significantly impact respiratory function. The diaphragm is the primary muscle involved in respiration, and when it is displaced, it affects lung capacities.

The correct choice reflects that the displacement leads to a decrease in expiratory reserve volume. This volume represents the amount of air that can be forcibly exhaled after a normal exhalation. When the diaphragm is pushed upward by the expanded uterus, it reduces the space available for the lungs to expand, making it more difficult for air to be expelled completely from the lungs. Consequently, this reduced capacity to exhale fully contributes to a decrease in expiratory reserve volume.

The other options do not correctly describe the physiological changes that occur due to the displacement caused by the uterus. For instance, the functional reserve capacity typically decreases due to the upward displacement of the diaphragm, rather than increasing the inspiratory or expiratory reserve volumes. Thus, the displaced diaphragm leads to a limitation on the ability of the lungs to accommodate normal respiratory volumes, particularly in exhalation.