Low and Very Low Birthweight Infants

Publication Date:

Dec 07, 2018

Key facts about low and very low birthweight

  • The percentage of infants born with low birthweight remained relatively steady from 1996 to 2016, sitting between 7 and 8 percent.
  • In 2016, 14 percent of non-Hispanic black infants were born with low birthweight, compared with 8 percent of Asian/Pacific Islander and American Indian/Alaska Native infants, and 7 percent of non-Hispanic white and Hispanic infants.
  • In 2016, 14 percent of infants born to cigarette smokers had low birthweight, compared with 8 percent of infants born to nonsmokers.

Trends in low and very low birthweight infants

The percentage of infants who had low birthweight (weighing less than 2,500 grams, or 5.5 pounds) declined slightly from 1970 to 1980, from 8 to 7 percent of all births. The percentage then increased slowly but steadily to a peak in 2006, when it was again at 8 percent. Since then, the percentage has remained relatively steady. As of 2016, the percentage of infants with low birthweight remained at 8 percent (Appendix 1).

The percentage of infants with very low birthweight (weighing less than 1,500 grams, or 3.3 pounds) has increased slightly since 1980,1 but has stayed fairly consistent since the 1990s. One percent of infants born in 2016 had very low birthweight (Appendix 1).

Research indicates that the overall increase in low birthweight rates is partly the result of an increase in multiple births after 1980, although the rate among singleton births increased as well. In addition, improvements in technologies used to monitor at-risk pregnancies may have contributed to an increase in cesarean section deliveries and the number of low-weight births.2

Differences by race and Hispanic origin3

Non-Hispanic black infants are more likely than infants of other races to have low birthweight. In 2016, 14 percent of non-Hispanic black infants had low birthweight, compared with 8 percent of both Asian/Pacific Islander and American Indian/Alaska Native infants, and 7 percent of both non-Hispanic white and Hispanic infants. Additionally, the proportion of non-Hispanic black infants with very low birthweight was twice that of non-Hispanic white and Hispanic infants (2.9 percent versus 1.1 and 1.2 percent, respectively) (Appendix 1).

In 2016, among those of Hispanic origin, Puerto Rican infants had the highest rate of low birthweight (9 percent), while Mexican infants had the lowest rate (7 percent). In 2013 (the most recent year with such data available), Asian Indian infants had the highest rate of low birthweight among Asian and Pacific Islander infants (11 percent), followed by Filipino infants (9 percent). Among Asian and Pacific Islander infants, Chinese infants had the lowest rate of low birthweight, at 6 percent (Appendix 1).

Differences by maternal smoking status4

In 2016, 14 percent of infants born to cigarette smokers had low birthweight, compared with 8 percent of infants born to nonsmokers. A similar proportion can be seen in rates of very low birthweight (Appendix 1).

Differences by plurality of births

Infants from single births are much less likely than those from multiple births to have low birthweight. In 2016, 6 percent of infants from singleton births had low birthweight, compared with 57 percent of infants from multiple births. Similarly, 1 percent of infants from singleton births had very low birthweight, compared with 10 percent of infants from multiple births. The proportion of infants from multiple births that had low birthweight increased from 1990 to 2006, from 52 to 59 percent, but has since decreased slightly to 57 percent in 2016. The proportion of singleton births that had low birthweight stayed at about 6 percent throughout the 1990s, but increased slightly from 2000 to 2006, to 7 percent; the proportion has since fallen to 6 percent as of 2016 (Appendix 1).

Other estimates

State and local estimates

2016 state-level estimates of low birthweight rates by race and Hispanic origin are available from Martin, J. A., Hamilton, B. E., Osterman, M. J. K., Driscoll, A. K., & Drake, P. (2018). Births: Final data for 2016: Supplemental tables [Tables I-21 and I-22]. National Vital Statistics Reports, 67(1). Retrieved from https://www.cdc.gov/nchs/data/nvsr/nvsr67/nvsr67_01_tables.pdf.

State-level rate estimates for low birthweight and very low birthweight infants for 1996–2016 are also available from the KIDS COUNT Data Center at http://datacenter.kidscount.org/data#USA/2/27/28.

International Estimates

International estimates of low birthweight for 2011–2016 are available from UNICEF’s The State of the World’s Children 2016 at https://www.unicef.org/sowc2017/.

Data and appendices

Data source

• Data for 2012–2016: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics. (2018). CDC WONDER [Data tool]. Retrieved from http://wonder.cdc.gov/natality-current.html.
• Data for 2002–2011 and plurality data 1990–2013: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics. (2014). VitalStats [Data tool]. Retrieved from https://www.cdc.gov/nchs/data_access/vitalstatsonline.htm.
• Data for 1970–2001: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics. (2003). Health, United States, 2003 with Chartbook on Trends in the Health of Americans [Table 12]. Hyattsville, MD: Author. Retrieved from http://www.cdc.gov/nchs/data/hus/hus03.pdf.

Raw data source

Birth Data, National Vital Statistics System.
http://www.cdc.gov/nchs/births.htm

Appendices

Appendix 1. Percentage of Infants Born at a Low and Very Low Birthweight, By Selected Characteristics: Selected Years, 1970–2016

Background

Definition

Low birthweight refers to infants weighing less than 2,500 grams (5.5 pounds), and very low birthweight refers to infants weighing less than 1,500 grams (3.3 pounds). Estimates are based on live births with known birthweight, and exclude stillborn births and live births with unknown birthweight.

Citation

Child Trends. (2018). Low and Very Low Birthweight Infants. Retrieved from https://www.childtrends.org/indicators/low-and-very-low-birthweight-infants. 

Endnotes

1. Mathews, T. J. & MacDorman, M. F. (2005) Infant mortality statistics from the 2004 period linked birth/infant death data set. National Vital Statistics Reports, 55(14). Hyattsville, MD: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics. Retrieved from http://www.cdc.gov/nchs/data/nvsr/nvsr55/nvsr55_14.pdf.
2. Ibid.
3. Estimates for specific race groups have been revised to reflect the new OMB race definitions, and include only those who are identified with a single race. Hispanic infants may be of any race, while estimates for black and white infants do not include Hispanic infants.
4. Percent based on live births with known smoking status of mother and known birthweight. Some states are not included in the national estimates prior to 2002 because they did not require mothers to report tobacco use during pregnancy on birth certificates. Information on which states did not require mothers to report tobacco use each year can be found at http://www.cdc.gov/nchs/data/hus/hus03.pdf (see Appendix II, Tobacco use).