A low-birth-weight infant refers to a baby that is born weighing less than 5 pounds, 8 ounces. However, there are other terms that can be used to describe this condition. Another synonym for low-birth-weight infant is premature baby. Premature babies are born before the full term of pregnancy, which may cause them to have low birth weight. Another term that is closely related to low-birth-weight infant is small for gestational age (SGA) baby. An SGA baby is a newborn that has a weight lower than what is expected for their gestational age. Other synonyms include underweight baby, small baby, and mini baby. All these terminologies are used to describe a baby that is born with a low birth weight, which may require special care and attention.