Final answer:
A baby is at risk for Macrosomia due to gestational diabetes because the mother's high blood glucose levels can make the baby's pancreas produce extra insulin, leading to excessive growth.
Step-by-step explanation:
The reason a baby is at risk for Macrosomia in cases of gestational diabetes is that the condition can lead to excessive fetal growth. This occurs because the high blood glucose levels from the mother can cross the placenta, causing the baby's pancreas to produce extra insulin as a response. This excess insulin acts as a growth hormone, leading the baby to grow larger than normal.
Options A and B are incorrect because they relate to other complications of diabetes, such as kidney function and amniotic fluid levels, which are not directly associated with the development of Macrosomia.
Option C suggests the baby receives too much insulin from the mother, which is physiologically inaccurate as the baby produces its own insulin in response to the maternal glucose levels.