**Question:** Total lung capacity during pregnancy is

A. 90%
B. 80%
C. 100%
D. 70%

**Correct Answer:** C. 100%

**Core Concept:**
Total lung capacity (TLC) is the maximum amount of air that can be exhaled from the lungs after a deep inspiration. It is a crucial parameter in understanding respiratory physiology and its alterations in various conditions, including pregnancy.

**Why the Correct Answer is Right:**
Pregnancy is associated with various physiological changes that can impact respiratory function. One of the key changes is the increase in thoracic cage size, which results in an increase in lung volume. The increase in TLC during pregnancy (100%) is primarily due to the expansion of the thoracic cage and the soft tissues, including the diaphragm. This expansion allows for greater lung expansion, ultimately leading to an increase in TLC.

**Why Each Wrong Option is Incorrect:**

A. 90%: This option is incorrect because it suggests that pregnancy causes a significant reduction in TLC, which is not the case.
B. 80%: This option is incorrect because it underestimates the magnitude of TLC increase during pregnancy.
D. 70%: This option is incorrect as it inaccurately represents the TLC change during pregnancy.

**Clinical Pearl:**

Pregnancy-induced changes in lung function can lead to a host of respiratory complications in both the mother and fetus. Monitoring TLC, along with other respiratory parameters, during pregnancy is crucial to identify and manage such complications effectively.