<P> Low birth weight (LBW) is defined by the World Health Organization as a birth weight of a infant of 2,499 g or less, regardless of gestational age . Subcategories include very low birth weight (VLBW), which is less than 1500 g (3 pounds 5 ounces), and extremely low birth weight (ELBW), which is less than 1000 g (2 pounds 3 ounces). Normal weight at term delivery is 2500--4200 g (5 pounds 8 ounces--9 pounds 4 ounces). </P> <P> LBW is either caused by preterm birth (that is, a low gestational age at birth, commonly defined as younger than 37 weeks of gestation) or the infant being small for gestational age (that is, a slow prenatal growth rate), or a combination of both . </P>

What is the definition of low birth weight