Introduction It is a well-established fact that occasionally children are born at full term whose weight is below 2,500 gm. Such children are for practical reasons labeled as "premature" or "immature," and treated accordingly. The American Academy of Pediatrics recommends the following definition for prematurity: "A premature infant is one who weighs 2,500 gm. (5½ lb.) or less at birth regardless of the period of gestation,"1 and the World Health Organization recommends a birth weight of 2,500 gm. or less, regardless of estimated period of gestation and other criteria, as the definition of prematurity.2 This definition, which firmly relates prematurity to weight but not to gestational age, was established with the full knowledge that twins and other infants born after a gestation of 10 lunar months may weigh less than 2,500 gm. at birth. Practical reasons decided—and probably wisely so—that infants with a marked weight deficit should get