Low birth weight (LBW) infants may be born preterm (premature), at term but small for gestational age (SGA), or both preterm and SGA. LBW, very LBW (VLBW), extremely LBW (ELBW), and micropremie describe, respectively, those with birth weights of less than 2,500, 1,500, 1,000, or 800 grams. Premature and extremely premature infants are born before week 36 or 28 of gestation, respectively. Of LBW infants, about 70% are premature. Full-term SGA infants generally have suffered from intrauterine growth retardation (IUGR), suggesting that they have not achieved their full prenatal growth potential.