**Question:** Which cardiovascular change is physiological in the last trimester of pregnancy?

**Core Concept:** Cardiovascular adjustments in pregnancy

**Why the Correct Answer is Right:**

In the late stage of pregnancy, the human cardiovascular system undergoes several physiological changes to accommodate the increased blood volume and cardiac output required to meet the growing demands of the fetus and placenta. The primary change mentioned in the options is the **increase in cardiac output**.

**Why Each Wrong Option is Incorrect:**

A. **Decreased heart rate (HR)**: Although HR may decrease by approximately 2-4 beats per minute per week, this is not considered a significant change in the context of pregnancy. Therefore, this answer is incorrect.

B. **Increased venous return**: While venous return increases due to the decrease in systemic vascular resistance, this is not a unique feature of the last trimester, and the primary focus is on the increase in cardiac output during this stage.

C. **Increased cardiac output**: As mentioned earlier, this is the correct answer. The increase in cardiac output results from a combination of increased heart rate and stroke volume.

D. **Decreased systemic vascular resistance**: While systemic vascular resistance decreases in pregnancy, this answer is not as significant as the increase in cardiac output during the last trimester, making it a less relevant response to the question.

**Clinical Pearl / High-Yield Fact:**

During pregnancy, the heart adapts to the increased blood volume and cardiac output by dilating blood vessels and reducing systemic vascular resistance, which leads to peripheral edema in some cases.

**Correct Answer:** C. Increased cardiac output