This database report counts of live births occurring within the United States to U.S. residents and non-residents by state, county, child's gender and weight, mother's race, mother's age, mother's education, gestation period, and prenatal care.  Data are derived from birth certificates. Counties with fewer than 100,000 persons are combined together under the label "Unidentified Counties."  For confidentiality reasons, totals of 1-5 in counties are suppressed.  Data are not available for all counties.

Changes in demographic category classifications in 2010 make birth and fertility rates comparisions inconsistent with earlier years.  Users should exercise caution when comparing time series data because of this change. 

See additional documentation from the CDC for changes in some variables over time.