Birth Outcome Metadata: Low Birth Weight and Very Low Birth Weight


Birth certificate data used to calculate birth weight measures are from the Maine CDC, Office of Data, Research, and Vital Statistics (ODRVS).

Dates Available:

2000 - 2019

Geographic Resolution:

State, Public Health District, County


The Maine EPHT program receives birth certificate data annually from ODRVS. Low birth weight (<2500 grams) and very low birth weight (<1500 grams) births among Maine residents are analyzed, stratified by birth year, geographic resolution, birth event plurality, maternal age group, and infant sex. Low birth weight births are additionally restricted to only those live births occurring at 37 weeks of gestation or greater.

The dataset contains the following measures:

1. Percent of low birth weight births.
2. Percent of very low birth weight births.
3. Number of low birth weight births.
4. Number of very low birth weight births.


This data set supports efforts to improve public health in Maine and contributes to the U.S. CDC’s National Environmental Public Health Tracking (EPHT) Network. A key activity of participants in this network is to track and make available environmental health measures on state and national data portals. Measures derived from the data set described here can be used to compare low birth weight and very low birth weight births across the state, between groups of people, over time, and in relation to risk factors, exposures, and health outcomes.

The Maine Tracking Network, a member of the National EPHT Network, connects communities, public health professionals, policy makers, state agencies, and others to the data they need to monitor public health, respond to health concerns, prioritize resources for public health action, and evaluate prevention activities. Maine tracks certain health effects, exposures, and environmental hazards that have known relationships, as well as some health effects and environmental hazards that have suspected relationships. By making health and environmental data available through the Maine Tracking Network, more people have access to data they need to think critically and hypothesize about health outcomes and their relationships to conditions in the environment.

Supplemental Information:

Low birthweight is a birth outcome that affects all segments of a population and has multiple causes. The birthweight of a baby is directly related to the gestational age at which the child is born. Multiple births are usually low birth weight, even those delivered at full term (a gestational age of 37 weeks or more). The Maine EPHT program analyzes low birthweight and very low birthweight data by using plurality to identify singleton births from all births. Gestational age is used to identify full-term births.  Analyses based on full-term gestational age and/or singleton births distinguishes between preterm and multiple birth categories and decreased fetal growth that may be affected by other risk factors, including environmental factors.

Entity and Attribute Overview:

The dataset includes: birth year, geographic resolution, count, population, birth plurality, infant sex, maternal age group, percent and 95% confidence intervals.

Data Limitations:

  • There are uncertainties associated with the gestational age estimates that are used in some of the birth outcome analyses. In Maine, a clinical estimate of gestational age is recorded on the birth certificate, and this is used for gestational age estimates. Not all states include a clinician estimate and must use only information on the interval between the first day of the mother’s last normal menstrual period (LMP) and the day of birth to determine gestational age. Therefore there are differences in how gestational age is calculated across states.
  • Adoptive records may not have correct birth mother demographic information. It is possible that a birth record may arrive at the vital records with the birth mother’s demographic information only to be amended with the demographic characteristics of the adoptive mother.
  • Although there is universal reporting of live births and infant deaths in the U.S., some births/deaths may be excluded because of the difficulty in distinguishing a death shortly after birth as a live birth; a death soon after birth might be reported as a fetal death rather than as a live birth and infant death.
  • The most important information used to link birth outcomes to environmental exposures is the place of residence during pregnancy and the first year of life. The location information used refers to the mother's place of residence at birth, which does not always represent where the mother lived during pregnancy or where the infant lived.

Access Constraints:

Publicly available data are suppressed in accordance with the Maine CDC Privacy Policy to protect confidentiality.

More Information:

Suggested Citation for Data Displays:

Maine Center for Disease Control and Prevention, Maine Tracking Network. Birth Outcomes Metadata: Low Birth Weight. Available online:  Accessed on [date accessed].