What respiratory change occurs during pregnancy?

During pregnancy, there is a significant physiological adaptation in the respiratory system to accommodate both the mother and the developing fetus. One of the primary changes is the increase in tidal volume, which refers to the amount of air inhaled or exhaled during a normal breathing cycle. This increase is a response to heightened metabolic demands, as the growing fetus requires more oxygen and produces more carbon dioxide, which the mother's body needs to eliminate.

Increased tidal volume aids in improving overall oxygenation, as it allows for greater air exchange in the lungs. This adaptation aligns with the overall respiratory demands during pregnancy, where it’s crucial for the mother to ensure adequate oxygen supply for not only herself but also her baby.

In contrast, decreased tidal volume and decreased chest circumference would not support these needs and are not typical changes observed during pregnancy. Additionally, increased airway resistance can occur due to physiological changes, such as increased progesterone levels affecting smooth muscle, but it does not directly correspond with the requirement for increased overall air exchange. Thus, the correct choice reflects the body's adaptation to effectively manage the increased oxygen demands during this critical period.