APA Dictionary of Psychology

infant weight at birth of less than 5.5 pounds (2,500 g) regardless of gestational age. Very low birth weight (VLBW) refers to weight of less than 3.5 pounds (1,500 g) and extremely low birth weight (ELBW) is used to describe an infant weight of less than 2.2 pounds (1,000 g) at birth. Children born with VLBW are at an increased risk for serious health problems and reduced scores on measures of intelligence. Children born with moderately low birth weight (i.e., 1,500–2,499 g, 3.5–5.8 lbs) are at risk for similar, albeit less severe, outcomes. However, the research base is far less available within the moderate low birth weight category. The vast majority of studies have focused on the VLBW and ELBW categories. These categories encompass only 15% of all low weight births and approximately 1.2% of all births in a given year. Compare small for gestational age.