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 pounds, 8 ounces) are at higher risk of early death and long-term health and developmental issues than infants born later in pregnancy or at higher birthweights.25, 26, 27 Many but not all preterm infants are born with low birthweight (and vice versa). Although the increasing multiple birth rate since 1980 contributed to the rise in preterm birth and low birthweight infants, preterm birth and low birthweight levels also increased substantially among singleton births.23 Disorders related to preterm birth and low birthweight are the second leading cause of infant death in the United States.25 Preterm birth and low birthweight vary by maternal race and Hispanic origin, and maternal age.

Figure 15. Percentage of infants born preterm by maternal race and Hispanic origin, 2016–2022
Percentage of infants born preterm by maternal race and Hispanic origin, 2016–2022

NOTE: NH = non-Hispanic origin; AIAN = American Indian or Alaska Native; NHOPI = Native Hawaiian or Other Pacific Islander. The obstetric estimate of gestation at delivery is used to estimate the gestational age of a newborn. Infants born at less than 37 weeks of gestation are considered preterm. Race and Hispanic origin refer to the mother's race and Hispanic origin. The 1997 U.S. Office of Management and Budget standards for data on race and ethnicity were used to classify people into one of the following five racial groups: White, Black or African American, Asian, American Indian or Alaska Native, or Native Hawaiian or Other Pacific Islander. All categories are single race. Data on race and Hispanic origin are collected and reported separately. People of Hispanic origin may be of any race.

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

  • The percentage of infants born preterm increased from 9.8% in 2016 to 10.4% in 2022.
  • From 2016 to 2022, the percentage of infants born preterm increased for Black, non-Hispanic, White, non-Hispanic, and Hispanic women but did not change significantly for the other race and Hispanic origin groups.
  • From 2021 to 2022, the percentage of infants born preterm decreased for Black, non-Hispanic women and Hispanic women but did not change significantly for the other race and Hispanic origin groups.
  • In 2022, infants of Black, non-Hispanic women (14.6%) were the most likely to be born preterm, followed by infants of American Indian or Alaska Native, non-Hispanic (12.6%) and Native Hawaiian or Other Pacific Islander, non-Hispanic (12.0%) women. Infants of Hispanic (10.1%), White, non-Hispanic (9.4%), and Asian, non-Hispanic (9.2%) women were less likely to be born preterm.
  • Throughout the period, Black, non-Hispanic women were the most likely to have a preterm birth.

Figure 16. Percentage of infants born with low birthweight by maternal age, 2016–2022
Percentage of infants born with low birthweight by maternal age, 2016–2022

NOTE: Infants born at less than 2,500 grams or 5 pounds, 8 ounces are considered low birthweight. Live births with unknown birthweight are excluded.

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

  • The total percentage of infants born with low birthweight remained stable from 2016 to 2022.
  • From 2016 to 2022, the percentage of infants born with low birthweight varied by age group. For ages 25–29, the percentage increased over the whole period. For ages 20–24 and 35–39, the percentage increased from 2020 to 2022. For women 40 and over, the percentage declined from 2016 to 2020 and then was stable through 2022. The trend remained stable for the other age groups.
  • In 2022, the percentage of infants born with low birthweight was highest for women age 40 and over (11.3%), followed by adolescents ages 15–19 (10.9%) and women ages 20–24 (9.1%) and 35–39 (9.0%). Women ages 25–29 and 30–34 (8.0% each) were the least likely to have an infant born with low birthweight.
  • Throughout the period, women age 40 and over and adolescents ages 15–19 were the most likely to have an infant born with low birthweight.

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23 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:122047.

25 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.

26 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.

27 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.

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