What is low birthweight? Low birthweight is a term used to
describe babies who are born weighing less than 2,500 grams (5
pounds, 8 ounces). In contrast, the average newborn weighs about
8 pounds. Over 8 percent of all newborn babies in the United
States have low birthweight. The overall rate of these very
small babies in the United States is increasing. This is
primarily due to the greater numbers of multiple birth babies
who are more likely to be born early and weigh less. Over half
of multiple birth babies have low birthweight compared with only
about 6 percent of single birth babies. Babies with low
birthweight look much smaller than other babies of normal
birthweight. A low birthweight baby's head may appear to be
bigger than the rest of the body and he or she often looks thin,
with little body fat. What causes low birthweight? The primary
cause of low birthweight is premature birth (being born before
37 weeks gestation). Being born early means a baby has less time
in the mother's uterus to grow and gain