**Core Concept**
Diabetic pregnancy is a complex condition that involves the management of both maternal and fetal health. The complications associated with diabetes in pregnancy can be broadly categorized into short-term and long-term effects. The short-term complications include macrosomia, polyhydramnios, pre-eclampsia, and preterm labor, while the long-term effects include an increased risk of congenital anomalies.

**Why the Correct Answer is Right**
Diabetic pregnancy is associated with various complications, but the least common among them is congenital rubella syndrome. This is because rubella is a preventable infection through vaccination, and most women of childbearing age are immunized against it. However, diabetic pregnancies are still at an increased risk of congenital anomalies due to the teratogenic effects of hyperglycemia.

**Why Each Wrong Option is Incorrect**
* **Option A:** Congenital anomalies are a significant concern in diabetic pregnancies, and the most common ones include cardiac defects, neural tube defects, and cleft palate.
* **Option B:** Macrosomia is a common complication of diabetic pregnancies, occurring in up to 20% of cases. It is caused by the excessive insulin resistance and hyperglycemia in the mother.
* **Option C:** Pre-eclampsia is a common complication of diabetic pregnancies, occurring in up to 20% of cases. It is caused by the endothelial dysfunction and abnormal angiogenesis in the placenta.

**Clinical Pearl / High-Yield Fact**
It is essential to emphasize the importance of preconception counseling and tight glycemic control in diabetic pregnancies to minimize the risk of congenital anomalies and other complications.

**Correct Answer: D. Congenital rubella syndrome.**