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America's Children: Key National Indicators of Well-Being, 2013

Preterm Birth and Low Birthweight

Infants born preterm (less than 37 completed weeks of gestation) or with low birthweight (less than 2,500 grams or 5 lbs. 8 oz.) are at higher risk of early death and long-term health and developmental issues than infants born later in pregnancy or at higher birthweights.114,115,116 Many, but not all, preterm infants are also low birthweight, and vice versa. In 2010, infants born preterm accounted for two-thirds of all low birthweight infants, and over 40 percent of preterm births were low birthweight.6 Preterm infants born at less than 34 weeks (early preterm) are at high risk for poor outcomes, including chronic health conditions, long-term disability, and death. The majority of preterm births are infants born at 34–36 weeks (late preterm). Late preterm infants are at lower risk of poor outcomes than infants born earlier but are at higher risk than infants delivered at term or later.114 Disorders related to preterm birth and low birthweight are the second leading cause of infant death in the United States.114

Indicator Health1.A: Percentage of infants born preterm and percentage of infants born with low birthweight, 1990–2011
Percentage of infants born preterm and percentage of infants born with low birthweight, 1990–2011

NOTE: Data for 2011 are preliminary. Late preterm infants are born at 34–36 weeks of gestation; early preterm infants are born at less than 34 weeks of gestation. Moderately low birthweight infants weigh 1,500–2,499 grams at birth; very low birthweight infants weigh less than 1,500 grams at birth.

SOURCE: National Center for Health Statistics, National Vital Statistics System.

  • The percentage of infants born preterm declined for the 5th straight year in 2011, to 11.7 percent, down from a high of 12.8 percent in 2006. The percentage of infants born with low birthweight was 8.1 in 2011, down from 8.3 percent in 2006.
  • The percentage of preterm and low birthweight infants had been on the rise for several decades. From 1990 to 2006, the percentage of preterm births rose from 10.6 to 12.8 percent. The increase in late preterm births (from 7.3 to 9.1 percent) accounted for most of this change. The percentage of births that were early preterm rose from 3.3 to 3.7 percent over this period.
  • The percentage of infants born with low birthweight rose from 7.0 percent of all births in 1990 to 8.3 percent in 2006. The percentage of very low birthweight infants was 1.4 percent in 2011, down slightly from the high of 1.5 percent reported for 2004 to 2009. The percentage of moderately low birthweight infants rose from 5.7 to 6.8 percent from 1990 to 2006, declined slightly, to 6.7, in 2007, and has been unchanged since.
  • The increasing multiple birth rate was a contributing factor to the rise in preterm birth and low birthweight from 1990 to 2006. However, preterm and low birthweight levels rose substantially among singleton births as well.6 Declines in singleton preterm birth and low birthweight rates since 2006 are similar to those for all births.

Indicator Health1.B: Percentage of infants born with low birthweight by race and Hispanic origin of mother, 1990, 2006, and 2011
Percentage of infants born with low birthweight by race and Hispanic origin of mother, 1990, 2006, and 2011

NOTE: Data for 2011 are preliminary. Race refers to mother's race. The 1977 Office of Management and Budget (OMB) standards for data on race and ethnicity were used to classify persons into one of the following four racial groups: White, Black, American Indian or Alaskan Native, or Asian or Pacific Islander. Although state reporting of birth certificate data is transitioning to comply with the 1997 OMB standard for race and ethnicity statistics, 2006 and 2010 data from states reporting multiple races were bridged to the single-race categories of the 1977 OMB standards for comparability with other states. Data on race and Hispanic origin are collected and reported separately. Persons of Hispanic origin may be of any race.

SOURCE: National Center for Health Statistics, National Vital Statistics System.

  • Among racial and ethnic groups, Black, non-Hispanic women were the most likely to have a low birthweight infant in 2011 (13.3 percent, compared with 7.1 percent for White, non-Hispanic, 7.5 percent for American Indian/Alaskan Native, 8.3 percent for Asian or Pacific Islander, and 7.0 percent for Hispanic mothers). Similar differences in low birthweight by race and ethnicity were observed in previous years.
  • Low birthweight levels fluctuated for Black, non-Hispanic births in recent years, ranging from lows of 13.1 to 13.2 percent for 1995 to 2001, to a high of 14.0 percent in 2005 and 2006. The 2011 percentage was 13.3 percent, the same as that for 1990. Among White, non-Hispanic infants, the percentage of low birthweight infants rose from 5.6 percent in 1990 to 7.3 percent in 2006, and declined to 7.1 percent in 2011. The percentage of low birthweight Hispanic infants rose between 1990 and 2006 (from 6.1 to 7.0 percent), and was 7.0 percent in 2011. Between 1990 and 2006, low birthweight percentages increased for American Indian or Alaskan Native infants (from 6.1 to 7.5 percent) and Asian or Pacific Islander infants (from 6.5 to 8.1 percent). In 2011, some 7.5 percent of American Indian or Alaskan Native infants were low birthweight, essentially unchanged since 2006. The percentage of Asian or Pacific Islander infants who were low birthweight increased from 8.1 percent in 2006 to 8.3 percent in 2011.
  • In 2011, as in earlier years, Black, non-Hispanic women were more likely to have a preterm birth (16.8 percent) than White, non-Hispanic (10.5 percent) and Hispanic (11.7 percent) women.
  • The 2011 percentage of Black, non-Hispanic infants born preterm (16.8 percent) was the lowest reported in the three decades for which comparable data are available. The percentage of preterm Black, non-Hispanic births declined from 19.0 percent in 1991 to 17.4 percent in 2000, rose to 18.5 percent in 2006, but has declined fairly steadily since (16.8 percent in 2011). From 1990 to 2006, the percentage of preterm births increased steadily for White, non-Hispanic infants (from 8.5 to 11.7 percent), but has since declined reaching 10.5 percent in 2011. The percentage of preterm Hispanic infants increased from 11.0 to 12.3 percent between 1990 and 2007, but declined to 11.7 in 2011.

table icon HEALTH1.A HTML Table, HEALTH1.B HTML Table

6 Martin, J.A., Hamilton, B.E., Ventura, S.J., Osterman, M.J.K., Wilson, E.C., and Mathews, T.J. (2012). Births: Final data for 2010. National Vital Statistics Reports 61(1). Hyattsville, MD: National Center for Health Statistics.

114 Mathews, T.J., and MacDorman, M.F. (2012). Infant mortality statistics from the 2008 period linked birth/infant death data set. National Vital Statistics Reports, 60(5) Hyattsville, MD: National Center for Health Statistics.

115 Institute of Medicine, Committee on Understanding Premature Birth and Assuring Healthy Outcomes and Board on Health Sciences Policy. (2005). Preterm birth: Causes, consequences, and prevention. Washington, DC: The National Academies Press.

116 Hack, M., Taylor, H.G., Droter, D., Schluchter, M., Cartar, L., Andreias, L., Wilson-Costello, D., and Klein, N. (2005). Chronic conditions, functional limitations, and special health care needs of school-aged children born with extremely low birthweight in the 1990s. Journal of the American Medical Association, 294: 318–325.