**Core Concept**
Infants born to diabetic mothers are at an increased risk of congenital heart defects, primarily due to the teratogenic effects of maternal hyperglycemia on fetal development. The most common cardiac anomaly in this population is a result of abnormal fetal cardiac morphogenesis.

**Why the Correct Answer is Right**
Transposition of great arteries (TGA) is a congenital heart defect where the two main arteries that carry blood out of the heart are reversed, leading to oxygenated and deoxygenated blood being circulated in opposite directions. This anomaly occurs in approximately 5-7% of infants born to diabetic mothers, making it the most common cardiac defect in this population. The pathogenesis of TGA in diabetic mothers is thought to be related to the abnormal expression of genes involved in cardiac development, which are sensitive to fluctuations in maternal glucose levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Coarctation of the aorta is a narrowing of the aortic isthmus, which can occur in infants of diabetic mothers, but it is not the most common cardiac anomaly in this population.
**Option B:** Fallot's tetralogy is a cyanotic congenital heart defect characterized by four components: ventricular septal defect, pulmonary stenosis, right ventricular hypertrophy, and an overriding aorta. While it can occur in infants of diabetic mothers, it is not as common as TGA.
**Option C:** Ebstein's anomaly is a rare congenital heart defect characterized by an abnormal formation of the tricuspid valve and right ventricle. It is not typically associated with maternal diabetes.

**Clinical Pearl / High-Yield Fact**
Infants of diabetic mothers are also at increased risk of other congenital anomalies, including neural tube defects, limb abnormalities, and gastrointestinal malformations. Therefore, a detailed prenatal ultrasound and postnatal evaluation are essential to identify and manage these complications promptly.

**✓ Correct Answer: D. Transposition of great arteries**