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Low Birth Weight


Low birth weight is a leading cause of neonatal mortality (death before 28 days of age). Low birth weight infants are more likely to experience physical and developmental health problems or die during the first year of life than are infants of normal weight.1,2

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 2009. In 2006, the rate of low birth weight was the highest recorded in four decades (8.3 percent). The increase in multiple births, which are at high risk of low birth weight, strongly influenced this increase; however, rates of low birth weight also rose for singleton births.3

In 2009, the rate of low birth weight was much higher among infants born to non-Hispanic Black women (13.6 percent) than infants born to mothers of other racial/ethnic groups. The second highest rate, which occurred among Asian/Pacific Islanders, was 8.3 percent, followed by a rate of 7.3 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). Low birth weight levels in 2009 were not significantly different from 2008 for non-Hispanic White, non-Hispanic Black, and Hispanic infants.

Low birth weight also varied by maternal age. In 2008 (the latest year for which data are available), the rate of low birth weight was highest among babies born to women younger than 15 years of age (12.4 percent), followed by babies born to women aged 40–54 years (11.8 percent). The lowest rates occurred among babies born to mothers aged 25–29 years and 30–34 years (7.4 and 7.6 percent, respectively).

1 Stein REK, Siegel MJ, Bauman LJ. Are children of moderately low birth weight at increased risk for poor health? A new look at an old question. Pediatrics 2006;118: 217-223.
2 Matthews TJ, MacDorman MF. Infant mortality statistics from the 2006 period linked birth/infant death data set. National vital statistics reports; vol 58 no 17. Hyattsville, MD: National Center for Health Statistics. 2010.
3 Martin JA, Hamilton BE, Sutton PD, Ventura SJ, et al. Births: Final data for 2006. National vital statistics reports; vol 57 no 7. Hyattsville, MD: National Center for Health Statistics. 2009.


This image is described in the Data section.

infant low birthweight by maternal race graph


Low Birthweight Among Infants, by Maternal Race/Ethnicity, 1990–2009*

Percent of infants for:

  • Non-Hispanic Blacks increased from approximately 13.2 to 13.6
  • All Races increased from approximately 7.0 to 8.2
  • Asian/Pacific Islanders** increased from approximately 6.2 to 8.3
  • American Indian/Alaska Natives increased from approximately 6.0 to 7.3
  • Non-Hispanic Whites increased from approximately 5.7 to 7.2
  • Hispanics increased from approximately 6.0 to 6.9

*Data for 2009 are preliminary.
**Separate estimates for Asians and Native Hawaiians and Other Pacific Islanders were not available.

Source: Hamilton BE, Martin JA, Ventura SJ. Births: Preliminary data for 2009. National vital statistics reports web release; vol 59 no 3. Hyattsville, MD: National Center for Health Statistics. 2010. Accessed March 2011.

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