**Core Concept**
A normal pregnancy is characterized by a series of physiological changes that support fetal growth and development. One of these changes is the increase in maternal body weight, which is influenced by the growth of the fetus, placenta, and amniotic fluid, as well as changes in maternal body composition.

**Why the Correct Answer is Right**
The normal net weight gain during pregnancy is approximately 24 pounds, as recommended by the Institute of Medicine (IOM). This weight gain is essential for fetal growth and development, as well as for the mother's health and well-being. The weight gain is primarily due to the increase in the size of the uterus, the growth of the fetus, and the accumulation of fat stores. The recommended weight gain varies depending on the mother's pre-pregnancy body mass index (BMI), with underweight women requiring more weight gain and overweight women requiring less.

**Why Each Wrong Option is Incorrect**
* **Option A:** 11 Pounds – This is an underestimation of the normal weight gain during pregnancy, which would not provide adequate nutrition and energy for fetal growth and development.
* **Option C:** 36 Pounds – This is an overestimation of the normal weight gain, which could increase the risk of gestational diabetes and hypertension.
* **Option D:** 42 Pounds – This is an extreme overestimation of the normal weight gain, which could lead to significant maternal morbidity and mortality.

**Clinical Pearl / High-Yield Fact**
A healthy weight gain during pregnancy is crucial for fetal growth and development, as well as for the mother's health and well-being. Women with a pre-pregnancy BMI below 18.5 should aim for a weight gain of 28-40 pounds, while women with a pre-pregnancy BMI above 25 should aim for a weight gain of 15-25 pounds.

✓ Correct Answer: B. 24 Pounds