## **Core Concept**
Cardiac output (CO) is the volume of blood the heart pumps per minute. During pregnancy, CO increases significantly due to various physiological changes. The maximum cardiac output is achieved at a specific gestational age.

## **Why the Correct Answer is Right**
The maximum cardiac output during pregnancy is observed at around **28-32 weeks of gestation**. This increase is primarily due to the combined effects of increased stroke volume and heart rate. The increase in CO starts early in pregnancy, peaks in the late second to early third trimester, and then returns to near pre-pregnancy levels by term.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because cardiac output starts increasing early in pregnancy but does not reach its peak in the first trimester.
- **Option B:** This option is incorrect as cardiac output continues to increase beyond the first trimester and does not peak until later.
- **Option D:** This option is incorrect because by term (around 37-42 weeks), cardiac output has started to decrease from its peak.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that cardiac output increases by approximately **40-50%** above non-pregnant levels by the late second to early third trimester. This significant increase supports the oxygenation and nutrient supply needs of the mother, fetus, and placenta.

## **Correct Answer:** . 28-32 weeks of gestation