Why do we measure low birthweight?
Low birthweight and its related complications are leading causes of infant death in the first year of life.(1,2) Babies born at a low birthweight who survive their infant years are more likely to experience long-term physical health problems and cognitive development challenges later in life.(3)
Causes of low birthweight include premature birth (born before 37 weeks’ gestation), restricted growth in the fetus due to maternal high blood pressure, maternal smoking or exposure to tobacco smoke, and insufficient maternal weight gain.(4,5) Teen pregnancy, older maternal age, and fertility treatments that lead to multiple births are also associated with low birthweight.(4,6) There are significant demographic differences in low birthweight prevalence, with babies born to Black persons more likely to be low birthweight compared to babies born to white, non-Hispanic persons. This disparity has been linked to the chronic stress that Black persons experience resulting from racism and other social inequalities.(3,7,8)
How do we measure low birthweight?
This metric includes any infant who is born alive with a birthweight of less than 2,500 grams.
Strengths of Metric
Limitations of Metric
Low birthweight can help us measure current status of infant health, maternal health, and future health.
Low birthweight is an indicator for long-term maternal malnutrition, inadequate prenatal care, and poor health care-delivery during pregnancy.
This metric does not separate babies born at a very low birthweight (<1,500 grams), who have even more severe health and mortality outcomes, from babies who weigh between 1,500-2,500 grams.(1,2)
Low birthweight is calculated by the following formula:
Low birthweight = [Infants with birthweight<2500 g]/Total live births x 100%
This metric was calculated by aggregating estimates from smaller geographies to the congressional district level. For more information, please refer to the Congressional District Health Dashboard Technical Document.
Estimates for this metric are from Natality Datafrom the National Vital Statistics System of the National Center for Health Statistics.
Matthews TJ, MacDorman MF, Thoma ME. Infant Mortality Statistics From the 2013 Period Linked Birth/Infant Death Data Set. National vital statistics reports : from the Centers for Disease Control and Prevention, National Center for Health Statistics, National Vital Statistics System. 2015;64(9):1-30.
Wise PH. The anatomy of a disparity in infant mortality. Annu Rev Public Health. 2003;24:341-362.
March of Dimes. Low Birthweight. https://www.marchofdimes.org/complications/low-birthweight.aspx. Updated October, 2014. Accessed February 22, 2018.
Valero de Bernabé J, Soriano T, Albaladejo R, et al. Risk factors for low birth weight: a review. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2004;116(1):3-15.
Johnson CD, Jones S, Paranjothy S. Reducing low birth weight: prioritizing action to address modifiable risk factors. Journal of Public Health. 2017;39(1):122-131.
Stanford JB, Simonsen SE, Baksh L. Fertility treatments and adverse perinatal outcomes in a population-based sampling of births in Florida, Maryland, and Utah: a cross-sectional study. BJOG : an international journal of obstetrics and gynaecology. 2016;123(5):718-729.
Kleinman JC, Kessel SS. Racial differences in low birth weight. Trends and risk factors. The New England journal of medicine. 1987;317(12):749-753.
Collins JW, David RJ, Handler A, Wall S, Andes S. Very Low Birthweight in African American Infants: The Role of Maternal Exposure to Interpersonal Racial Discrimination. American Journal of Public Health. 2004;94(12):2132-2138.
Last updated: January 24, 2023