Which of the following increases significantly as pregnancy advances?
**Core Concept**
Blood volume increases during pregnancy due to the increase in maternal cardiac output and the demands of the growing fetus. This is a crucial physiological adaptation to ensure adequate oxygenation and nutrient delivery to the fetus.
**Why the Correct Answer is Right**
The increase in blood volume is a gradual process that occurs throughout pregnancy, with a significant increase observed by the 28th week. This is mediated by the increase in maternal cardiac output, which is a result of the increased demand for oxygen and nutrients by the growing fetus. The increase in blood volume is also accompanied by an increase in maternal plasma volume, which leads to a dilutional anemia. The increased blood volume helps to meet the oxygen and nutrient demands of the fetus and prepares the mother for the demands of labor and delivery.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the physiological changes occurring during pregnancy. While there are changes in maternal metabolism and glucose utilization, they are not directly related to the increase in blood volume.
**Option B:** This option is incorrect because it refers to a decrease in blood volume, which is the opposite of what occurs during pregnancy.
**Option C:** This option is incorrect because it does not accurately describe the physiological changes occurring during pregnancy. While there are changes in maternal cardiac output, they are not directly related to the increase in blood volume.
**Clinical Pearl / High-Yield Fact**
It is essential for obstetricians and healthcare providers to monitor blood volume and maternal cardiac output during pregnancy to ensure adequate oxygenation and nutrient delivery to the fetus. This can be achieved through regular prenatal check-ups and monitoring of maternal vital signs.
**Correct Answer: C. Blood volume.**