Which of the following changes in lung volumes is typically decreased during pregnancy?

During pregnancy, changes in lung volumes are influenced by various physiological adaptations as the body accommodates the growing fetus. The correct answer, functional residual capacity, is typically decreased during pregnancy due to a couple of key factors.

As the uterus expands, it displaces the diaphragm upward, leading to a reduction in the thoracic cavity's ability to hold air. This displacement reduces the volume of air remaining in the lungs after normal expiration, which is what functional residual capacity represents. While other lung volumes such as tidal volume and inspiratory capacity may actually increase, functional residual capacity decreases because of this increased upward pressure from the diaphragm along with a shift in overall lung mechanics.

In understanding the other options, tidal volume generally increases during pregnancy as the body adapts to meet the higher oxygen demands. Inspiratory capacity can also increase as the body compensates for the increased need for air intake. Vital capacity is typically unchanged during pregnancy; even if the lung volumes of inspiratory and expiratory components change, vital capacity remains stable due to a balance of these changes.