**Core Concept**
Diabetes in pregnancy can lead to various fetal complications due to hyperglycemia-induced metabolic changes. The fetus may experience an increased insulin resistance and hyperinsulinemia, leading to altered growth patterns.

**Why the Correct Answer is Right**
The correct answer refers to the phenomenon of macrosomia, where the fetus grows excessively due to the increased glucose supply from the mother's blood. This is caused by the fetal pancreas producing excess insulin in response to the high glucose levels. The insulin stimulates the growth of the fetus, leading to an increased birth weight. This condition increases the risk of complications during delivery, such as shoulder dystocia and birth asphyxia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the effects of diabetes on the fetus. While it may be a potential complication of pregnancy, it is not the most relevant answer choice in this context.
**Option B:** This option is not a direct consequence of fetal hyperinsulinemia. While it may be related to fetal growth, it is not the most accurate answer choice.
**Option C:** This option is not a direct effect of diabetes on the fetus. While it may be a potential complication of pregnancy, it is not the most relevant answer choice in this context.

**Clinical Pearl / High-Yield Fact**
To remember the effects of diabetes on fetal growth, think of the "Bigger Baby" - macrosomia is a common complication of maternal diabetes.

**Correct Answer: C. Macrosomia.**