**Core Concept:** Small for gestational age (SGA) is defined as a newborn with a birth weight below the 10th percentile for gestational age. Various factors contribute to SGA, including maternal factors, placental factors, and fetal factors. Healthy pregnancies with normal placentation and fetal growth are less likely to result in SGA.

**Why the Correct Answer is Right:** The correct answer, D, refers to a "healthy pregnancy with normal placentation and fetal growth." Healthy pregnancies typically have proper placentation, which ensures adequate nutrient and oxygen supply to the fetus, promoting normal growth. This results in a newborn with a birth weight within the appropriate gestational age percentiles.

**Why Each Wrong Option is Incorrect:**

A. Malformations or chromosomal abnormalities: These conditions are associated with SGA, not increased birth weight.
B. Poor maternal nutrition: Malnutrition in the mother can lead to SGA, not increased birth weight.
C. Placenta previa: This placental abnormality increases the risk of SGA due to compromised fetal growth.

**Clinical Pearl:** Understanding the factors contributing to SGA helps healthcare professionals identify and manage high-risk pregnancies and provide appropriate interventions to prevent adverse outcomes. Prompt recognition and management of placental abnormalities, malnutrition, and other risk factors are crucial to ensure optimal fetal growth and development.

**Correct Answer:** D. Healthy pregnancy with normal placentation and fetal growth is least likely to result in a newborn who is small for gestational age (SGA).