When an infant’s weight is less than 5.5 pounds, regardless of gestational age, he or she is considered to have low birth weight. Very low birth weight is defined as less than 3.5 pounds.
This indicator, measured at the child level, can be calculated as the number of infants born in the last year whose birth weight was less than 5.5 pounds, divided by the total number of infants born that year in a state/community.
The percentage of infants who had low birth weight declined between 1970 and 1980, from 7.9% to 6.8% of all births, but increased slowly, yet steadily until 2006, when it was at 8.3% of births. Since then, the percentage has decreased slightly, to 8% of births in 2016. Black infants are more likely than babies of other races to have low birth weight. In 2016, 14% of black infants had low birth weight, compared with 8% of both Asian and Pacific Islander and American Indian and Alaska Native, and 7% of white and Hispanic infants. Black infants are also more than twice as likely as other infants to be of very low birth weight (3% compared with 1% for infants of other races).
The Kids Count Data Center includes the most recent state-level information on low birth weight babies.
Population-level estimates are available at the community level. The Center for Disease Control Natality online databases report counts of live births occurring within the United States to U.S. residents and non-residents. Counts can be obtained by state and county, child's gender, and weight.
Low birth weight correlates with increased challenges in the realms of motor, social, and intellectual development, including increased risk of long-term disability. Children with lower birth weights tend to have lower IQs and are more likely to be enrolled in special education classes. They are also less likely to complete high school. Children of “very low birth weight” are at the highest risk for the complications described above.