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 lb 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.20, 113, 114 Many but not all preterm infants also are low birthweight, and vice versa. 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.113, 115 The majority of preterm births are infants born at 34–36 weeks (late preterm). Late preterm infants are at a lower risk of poor outcomes than infants born earlier but are at a higher risk than infants delivered at term or later.113 The increasing multiple birth rate was a contributing factor to the rise in preterm birth and low birthweight. However, preterm birth and low-birthweight levels also increased substantially among singleton births.8 Disorders related to preterm birth and low birth weight are the second leading cause of infant death in the United States.20

Indicator HEALTH1.A: Percentage of infants born preterm and percentage of infants born with low birthweight, 2011–2021
Indicator HEALTH1.A: Percentage of infants born preterm and percentage of infants born with low birthweight, 2011–2021

NOTE: 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. Gestational age is estimated using the obstetric estimate of gestational delivery. Data on low birthweight can be found in table HEALTH1.B at https://www.childstats.gov/americaschildren/tables/health1b.asp.

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

  • The percentage of infants born preterm (less than 37 weeks of gestation) was stable from 2011 to 2014 and then increased from 9.6% in 2014 to 10.5% in 2021.
  • The percentage of infants born late preterm (34–36 completed weeks of gestation) in 2021 was 8%, slightly up from 7% in 2011.
  • The percentage of infants born early preterm (less than 34 completed weeks of gestation) in 2021 was 2.8%, the same percentage as in 2011.
  • The percentage of infants born with low birthweight (less than 2,500 grams, or 5 lb 8 oz) increased from 8% in 2011 to 9% in 2021.
  • From 2011 to 2021, the percentage of infants born with moderately low birthweight increased (7.1% in 2021), while the percentage of infants born with very low birthweight decreased (1.4% in 2021).

Indicator HEALTH1.B: Percentage of infants born with low birthweight by race and Hispanic origin of mother, 2011 and 2021
Indicator HEALTH1.B: Percentage of infants born with low birthweight by race and Hispanic origin of mother, 2011 and 2021

† Data for Asian, NH and NHOPI, NH groups were not available in 2011.

NOTE: NH = non-Hispanic origin; AIAN = American Indian or Alaska Native; NHOPI = Native Hawaiian or Other Pacific Islander. Starting with 2016 data, race on birth records is available based on the 1997 Office of Management and Budget (OMB) standards and presented as single-race estimates (only one race was reported on the birth certificate). These estimates include separate estimates for Asian, NH and NHOPI, NH groups. Data before 2016 were tabulated according to the 1977 OMB standards and bridged to retain comparability across states as they transitioned from the 1977 standards to those of 1997. Single-race estimates for 2016 onward are not completely comparable with bridged-race estimates for earlier years, particularly for the smaller race categories. Persons of Hispanic origin may be of any race.

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

  • In 2021, Black, non-Hispanic women were the most likely to have a low-birthweight infant (15%) compared with Native Hawaiian and Other Pacific Islander, non-Hispanic (9%); Asian, non-Hispanic (9%); American Indian or Alaska Native, non-Hispanic (8%); Hispanic (8%); and White, non-Hispanic (7%) women.
  • From 2011 to 2021, the percentage of low-birthweight infants born to Black, non-Hispanic; American Indian or Alaska Native, non-Hispanic; and Hispanic women generally increased, whereas the percentage of low-birthweight infants born to White, non-Hispanic women decreased.

table icon HEALTH1A HTML Table | HEALTH1B HTML Table

8 Osterman, M. J. K., Hamilton, B. E., Martin, J. A., Driscoll, A. K., & Valenzuela, C.P. (2023). Births: Final data for 2021. National Vital Statistics Reports, 72(1). National Center for Health Statistics. DOI: https://dx.doi.org/10.15620/cdc:122047.

20 Ely, D. M., & Driscoll, A. K. (2022). Infant mortality in the United States, 2020: Data from the period linked birth/infant death file. National Vital Statistics Reports, 71(5). National Center for Health Statistics. DOI: https://dx.doi.org/10.15620/cdc:120700.

113 Institute of Medicine, Committee on Understanding Premature Birth and Assuring Healthy Outcomes and Board on Health Sciences Policy. (2007). Preterm birth: Causes, consequences, and prevention. The National Academies Press.

114 Vogel, J. P., Chawanpaiboon, S., Moller, A. B., Watananirun, K., Bonet, M., & Lumbiganon, P. (2018). The global epidemiology of preterm birth. Best Practice & Research Clinical Obstetrics & Gynaecology, 52, 3–12.

115 Eichenwald, E. C., & Stark, A. R. (2008). Management and outcomes of very low birth weight. New England Journal of Medicine, 358(16), 1700–1711.

Federal Interagency Forum on Child and Family Statistics

Explore

More Information

Contact