Definitions: Babies born with a gestational age of less than 37 completed weeks.
Birth certificates that did not report gestational age were not included in this tabulation. Puerto Rico and Virgin Islands are not included in the U.S. Average.
Data Source: Population Reference Bureau analysis of 2007 to 2010 data from the National Center for Health Statistics (NCHS). Child Trends analysis of 1990-2006 Natality MicroData files from Centers for Disease Control and Prevention, National Center for Health Statistics.
Data are provided for the 50 most populous cities according to the most
recent Census counts. Cities for which data is collected may change
Note: Maps use the natural break classification method, which reflects patterns
in the data by dividing the map into naturally occurring groups. Using statistical tools, this method
determines cut-off points for each group by identifying large gaps in data values.
Note: The District of Columbia, Puerto Rico and the U.S. Virgin Islands are
not included in maps and rankings because they are not states and therefore comparisons on many
indicators of child well being are not meaningful.