Which of the following is NOT right regarding respiratory function during late trimester of normal pregnancy?
**Core Concept**
Pregnancy-induced changes in respiratory function are crucial for understanding maternal and fetal health. During the late trimester, respiratory function is altered due to increased progesterone levels, which cause relaxation of the diaphragm and abdominal muscles.
**Why the Correct Answer is Right**
The late trimester of pregnancy is characterized by increased tidal volume and minute ventilation. This is due to the mechanical effects of the expanding uterus on the diaphragm and chest wall. The diaphragm is elevated, and the increased intra-abdominal pressure pushes the diaphragm upwards, reducing its excursion. However, the increased progesterone levels lead to relaxation of the abdominal muscles and diaphragm, resulting in increased lung volume and ventilation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because respiratory rate may actually decrease during late pregnancy due to increased tidal volume and minute ventilation, which compensates for the increased metabolic demands of the fetus.
* **Option B:** This option is incorrect because oxygenation and ventilation are maintained in late pregnancy, despite the mechanical changes, due to the increased respiratory drive and tidal volume.
* **Option C:** This option is incorrect because respiratory function is not significantly impaired in late pregnancy; rather, it is adapted to meet the increased metabolic demands of the fetus.
**Clinical Pearl / High-Yield Fact**
Pregnant women often experience shortness of breath due to the mechanical effects of the expanding uterus on the diaphragm and chest wall. However, this is not a sign of respiratory distress, but rather a normal adaptation to meet the increased metabolic demands of the fetus.
**Correct Answer:** C