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In 2002, 314,077 babies (7.8 percent of all live births) were of low birth weight, weighing less than 2,500 grams, or 5 pounds 8 ounces, at birth. This rate represented a slight increase from the previous year. The percentage of newborns born at low birth weight has risen steadily from a low of 6.7 percent in 1984 and is currently at the highest level recorded in the past 3 decades.

The highest rates of delivering a low birth weight infant are among mothers younger than 15 years and older than 45. Much of the incidence of low birth weight among older mothers (older than 44) is due to an increase in the proportion of multiple births, as the use of assisted reproductive technologies increases. Multiple births accounted for 24 percent of low birth weight infants in 2002 compared to only 15 percent in 1980. However, the low birth weight rate among singleton infants increased as well.

Although the non-Hispanic Black low birth weight has declined slightly from a high of 13.6 percent in 1991, it remains considerably higher than the rate for non-Hispanic White (6.9 percent) and Hispanic (6.5 percent) infants. In 2002, the percent of low birth weight infants born to smokers (12.2 percent) was substantially higher than among nonsmokers (7.5 percent). This significant differential has been consistently observed among both non-Hispanic Black and non-Hispanic White infants. Other factors associated with increased risk of low birth weight include maternal poverty and low levels of educational attainment.

Low birth weight is one of the leading causes of neonatal mortality. Low birth weight infants are more likely to experience long-term disability or to die during the first year of life than are infants of normal weight.

Graph: Low Birth Weight Among Infants[d]