Final answer:
A small for gestational age baby refers to a newborn who has not grown adequately in the womb, while an underweight preterm newborn specifically refers to a baby born before full term with a low birth weight. Both are at a higher risk for health complications and developmental delays.
Step-by-step explanation:
A small for gestational age baby refers to a newborn who has not grown adequately in the womb and is smaller than expected for their gestational age, regardless of whether they were born preterm or full term. An underweight preterm newborn, on the other hand, specifically refers to a baby who is born before the full term of 36-40 weeks and has a birth weight lower than 2.5 kg (5.5 lb).
Both a small for gestational age baby and an underweight preterm newborn are at a higher risk for health complications and developmental delays. Low birth weight can be caused by factors such as maternal undernutrition, intrauterine growth restriction, or preterm birth.