What is low birth weight?

Babies that weigh less than 2,500 grams (about 5.5 pounds) at birth are considered to have ‘low birth weight.’

Multiple factors may contribute to low birth weight including: gestational age, sex, smoking during pregnancy, lack of prenatal weight gain, and social and environmental factors like poverty and air pollution. These problems may cause growth restrictions early in the pregnancy (‘early onset’) or later in the pregnancy (‘late onset’). When and why the onset occurs impacts the effect on the developing fetus, and the prognosis for the baby.

Why is birth weight important?

Low birth weight is the second leading cause of infant mortality. Low birth weight is an important measure of child well-being because it is also associated with short- and long-term health outcomes such as increased risk of delayed motor and social development, and development of cardiovascular disease later in life. Being born with low birth weight has also been linked to an increased need for health care and higher health care costs. Rates of low birth weight have increased in recent years underscoring the need for increased attention.

To learn more about the birth weight data presented here, check out our Technical Dictionary.

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To learn more about low birth weight, visit the Oregon Health Authority (OHA), Public Health Division:

Please remember the following
  • The OCID Child Well-being Dashboard only includes children born in Oregon since 2001.
  • To display race and ethnicity categories consistently across multiple data sources, OCID currently combines information from vital statistics, education, Medicaid, and child welfare records. Visit our Race and Ethnicity Data Overview to learn more.
  • The Dashboard shows descriptive data, not causal relationships. In depth analyses are needed to understand why disparities or trends occur. OCID’s targeted analyses shed light on policy questions prioritized by the Governance Committee.

For more information about the details and limitations of the data, please visit our Technical Dictionary and Dataset Overview.

Ready to explore the data?

Use the interactive display below to discover how characteristics collected by state programs vary among groups of children with different well-being outcomes.


Data are a starting point for understanding children’s experiences; they do not fully describe an individual’s identity or experience.

Want to dive deeper?

Explore the interactive display below to investigate potential trends or disparities among groups of children with the same well-being outcome.


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Suggested citation: Center for Evidence-based Policy, Oregon Health & Science University. Birth weight dashboard. Oregon Child Integrated Dataset (OCID) website. https://www.ocid-cebp.org/outcome/birth-weight/. Published [inserted ‘display updated’ date].

The Center for Evidence-based Policy partners with the Center for Health Systems Effectiveness, also at Oregon Health & Science University, on dashboard analytics.