**Core Concept**
Infants "at risk" are those who are vulnerable to various health issues due to their developmental stage, environmental factors, or underlying medical conditions. This concept is crucial in pediatric medicine, as early identification and intervention can significantly impact their long-term health outcomes.

**Why the Correct Answer is Right**
To determine which option does not describe an infant "at risk," we need to evaluate each choice in the context of pediatric medicine. Infants "at risk" often have underlying medical conditions, are exposed to environmental hazards, or have a family history of health issues.

* **Option A:** Premature birth is a significant risk factor for infants, as it can lead to respiratory distress syndrome, intraventricular hemorrhage, and other complications.
* **Option B:** Low birth weight is associated with increased morbidity and mortality in infants, as they may have inadequate stores of glucose, protein, and other essential nutrients.
* **Option C:** Intrauterine growth restriction (IUGR) is a condition where the fetus does not grow at a normal rate inside the womb, increasing the risk of perinatal mortality and long-term health issues.
* **Option D:** Infants with a normal birth weight and gestational age, born to a healthy mother with no known medical conditions, are generally not considered "at risk."

**Why Each Wrong Option is Incorrect**
* **Option A:** Premature birth is a well-established risk factor for infants, as it can lead to various complications.
* **Option B:** Low birth weight is associated with increased morbidity and mortality in infants.
* **Option C:** IUGR is a condition that increases the risk of perinatal mortality and long-term health issues.

**Clinical Pearl / High-Yield Fact**
When assessing infants "at risk," it's essential to consider multiple factors, including prematurity, low birth weight, IUGR, and family history of medical conditions. A thorough evaluation can help identify potential health issues and guide early intervention.

**Correct Answer: D. Infants with a normal birth weight and gestational age, born to a healthy mother with no known medical conditions, are generally not considered "at risk."**