## **Core Concept**
The increase in cardiac output during pregnancy is a critical physiological adaptation to meet the increased metabolic demands of the mother and the fetus. This increase is primarily due to elevations in stroke volume and heart rate. Cardiac output starts rising early in pregnancy, peaks around the second trimester, and remains elevated until delivery.

## **Why the Correct Answer is Right**
The correct answer, , indicates that the cardiac output increases by approximately 40% above non-pregnant levels. This increase is attributed to several factors, including an increase in blood volume (which can rise by as much as 40-50% above non-pregnant levels), an increase in stroke volume due to enhanced ventricular contractility and preload, and a modest increase in heart rate. These changes are essential for ensuring adequate perfusion of vital organs and the placenta.

## **Why Each Wrong Option is Incorrect**
- **Option A:** - This option suggests a much lower increase in cardiac output than what is observed in pregnancy. An increase of just 10% does not accurately reflect the significant cardiovascular adaptations that occur.
- **Option B:** - While an increase of 20% is closer, it still underestimates the actual rise in cardiac output observed during pregnancy.
- **Option D:** - This option suggests a decrease or a minimal increase in cardiac output, which contradicts the well-established physiological increases in cardiac output during pregnancy.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that cardiac output increases significantly during pregnancy, peaking at around 28-32 weeks of gestation. This increase supports the higher metabolic demands and ensures adequate oxygenation and nutrient delivery to both the mother and the fetus. Clinicians must consider these changes when evaluating and managing pregnant women, especially those with pre-existing cardiovascular conditions.

## **Correct Answer:** .