**Core Concept**
Small for date (SFD) babies, also known as small for gestational age (SGA), are infants whose birth weight is below the 10th percentile for their gestational age. This condition can result from various factors, including intrauterine growth restriction (IUGR), placental insufficiency, and maternal health issues. The most common complications in SFD babies are related to their growth restriction and potential underlying causes.

**Why the Correct Answer is Right**
The most common complication in SFD babies is hypoglycemia. This occurs due to the limited glycogen stores and impaired glucose homeostasis in these infants. SFD babies have reduced insulin levels, decreased glucose production in the liver, and impaired glucose uptake in the tissues. This leads to hypoglycemia, which can be severe and potentially life-threatening if not promptly treated. The management of hypoglycemia in SFD babies involves close monitoring of blood glucose levels and administration of glucose or dextrose.

**Why Each Wrong Option is Incorrect**
**Option A:** Asphyxia - While asphyxia can occur in SFD babies, it is not the most common complication. Asphyxia is more commonly associated with preterm infants or those with congenital anomalies.

**Option B:** Congenital anomalies - Congenital anomalies are not directly related to the growth restriction in SFD babies. While SFD babies may have an increased risk of congenital anomalies, it is not the most common complication.

**Option C:** Renal problems - Renal problems can occur in SFD babies due to various factors, including IUGR and placental insufficiency. However, they are not the most common complication.

**Clinical Pearl / High-Yield Fact**
It is essential to monitor blood glucose levels in SFD babies, especially in the first few hours after birth, to prevent and manage hypoglycemia. This can be achieved through frequent glucose checks and administration of glucose or dextrose as needed.

**Correct Answer:** D. Hypoglycemia.