U.S. Department of Health and Human Services, Health Resources and Services Administration

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Low Birth Weight

Low birth weight is one of the leading causes of neonatal mortality (death before 28 days of age). 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.

According to preliminary data, 8.2 percent of infants were born low birth weight (less than 2,500 grams, or 5 pounds 8 ounces) in 2007; this represents a slight decrease from the rate recorded in 2006 (8.3 percent), which was the sixth consecutive year of increase and the highest rate recorded in four decades.

The increase in multiple births, more than half of which are delivered at less than 2,500 grams, has strongly influenced the increase in low birth weight; however, rates of low birth weight are also on the rise for singleton births.

In 2007, the low birth weight rate was much higher among infants born to non-Hispanic Black women (13.8 percent) than among infants of other racial/ethnic groups. The next highest rate, which occurred among infants born to Asian/Pacific Islanders, was 8.1 percent, followed by a rate of 7.5 percent among American Indian/Alaska Natives. Low birth weight occurred among 7.2 percent of infants born to non-Hispanic White women, while infants of Hispanic women experienced the lowest rate (6.9 percent). The low birth weight rate remained steady or decreased for infants born to mothers of all racial/ethnic groups in 2007.

Low birth weight also varied by maternal age. In 2006 (the latest year for which data are available), the rate of low birth weight was highest among babies born to women aged 40-54 years (20.3 percent), followed by babies born to women under 15 years of age (13.4 percent.) The lowest rates occurred among babies born to mothers aged 25-29 years and 30-34 years (7.5 and 7.6 percent, respectively; data not shown).

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