Learn More: Low Birth Weight

What does this mean?

Low Birth Weight is defined as a baby weighing less than 2,500 grams (5 pounds, 8 ounces) at birth. Multiples (twins, triplets, or higher) often are low birth weight, even at term (these births are included in the low birth weight statistics in the Hillsborough Community Atlas). There are two categories of low birth weight:

  • Preterm births (also called premature births) occur before the end of the 37th week of pregnancy. More than 60 percent of low birth weight babies are preterm.
  • Small-for-date babies ("small for gestational age" or "growth-restricted") may be full-term but are underweight. Their low birth weight results, at least partly, from slowing or temporary halting of growth in the womb.

Low birth weight can result from genetic conditions or environmental factors that limit normal development. A mother's medical problems also influence birth weight, especially if she has high blood pressure, certain infections or heart, kidney or lung problems. An abnormal uterus or cervix can increase the mother's risk of having a premature, low birth weight baby. The mother's behavior during pregnancy can influence the birth outcome. Behavior's such as alcohol or drug use, smoking, or poor nutrition can contribute to a low birth weight infant. Additionally, social factors such as housing, poverty, poor access to health care, lack of social support and their influence on the mother's level of stress can contribute to poor birth outcomes.

Why is it important?

Low birth weight affects about one in every thirteen babies born each year in the United States. It is a factor in 65 percent of infant deaths. Low birth weight babies may face serious health problems as newborns, and are at increased risk of long-term disabilities. Visual and auditory impairments, learning disorders, behavioral problems, grade retention, and school failure have been linked to low birth weight. Advances in newborn medical care have greatly reduced the number of infant deaths associated with low birth weight, as well as the number of disabilities survivors of low birth weight experience. Still, a small percentage of survivors are left with problems such as mental retardation, cerebral palsy and impairments in lung function, sight and hearing.

How are the data collected (methods)?

In Florida, this data is regularly collected and maintained by the State's Department of Children and Families.


Centers for Disease Control and Prevention
March of Dimes
Pathways Mapping Initiative

Caveats and Limitations

The birth data statistics presented are calculated spatially by first geocoding the addresses of the birth mothers. Geocoding involves matching a physical address to a digital reference layer, such as a roads or parcels layer, in GIS. Geocoding rarely results in a 100% successful matching rate and this holds true for the data being presented here as well. Residency addresses provided by the birth mother were geocoded directly by the Florida Department of Health. The percentage matched is typically very high (around 90%) and while this number serves as a very good representation of the birth trends within the county it is important to note that the data presented here is a sample of the true total number of births.

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