**Core Concept**
During pregnancy, the body undergoes various physiological changes to accommodate the growing fetus and prepare for childbirth. These changes involve the cardiovascular, respiratory, and gastrointestinal systems, among others. One of the notable changes is the increase in cardiac output, which is essential for meeting the increased oxygen and nutrient demands of the mother and the fetus.

**Why the Correct Answer is Right**
The correct answer is related to the increase in cardiac output. During pregnancy, the maternal heart rate increases, and the stroke volume also increases to meet the increased demand for oxygen and nutrients. This increase in cardiac output is mediated by the release of various hormones, including estrogen and progesterone, which cause the heart to work more efficiently. Additionally, the decrease in systemic vascular resistance due to the relaxation of smooth muscle cells in the blood vessels also contributes to the increase in cardiac output.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is not directly related to the physiological changes that occur during pregnancy.
* **Option B:** This option is incorrect because it is a potential complication of pregnancy, but not a physiological change that occurs normally.
* **Option D:** This option is incorrect because it is a potential cause of hypotension in pregnancy, but not a normal physiological change.

**Clinical Pearl / High-Yield Fact**
One important clinical pearl is to recognize that the increase in cardiac output during pregnancy is a normal physiological change, and it does not necessarily indicate any underlying pathology. However, it is essential to monitor the mother's cardiac function and blood pressure closely to ensure that there are no complications.

**Correct Answer:** C.