Regional Variations of Population Factors Affecting Birth Outcomes in the United States

Purpose: To analyze patterns of infant mortality (IMR), low birth weight (LBW), and population characteristics (preterm births, birth to teens, births to mothers with late or no prenatal care, and births to unmarried mothers) across the four geographic regions of the US (Northeast, Midwest, South, West). Data and Methods: Cross-sectional ecological analysis of year 2000 data derived from the Area Resource File and linked with the County Cartographic Boundary File (US Census). 3141 continental counties were analyzed. Mean values were computed and compared by US geographic region using Tukey's test with a significance level at 0.05. Graduated color maps were generated from normalized data, using Jenks' natural breaks classification. Results: The average IMR and proportion of LBW for the US were respectively 7.34 per 1,000 LB and 7.45 per 100 births. In the South, IMR (8.27 per 1,000 LB) and proportion of LBW (8.54 per 100 births) were significantly higher than in any other region. Similarly, for population risk factors, counties in the South presented significantly higher proportions of preterm births (13.03%), birth to teen mothers (6.28%), and births to unmarried mothers (35.24%) while the averages for the US were 11.62%, 4.90%, and 31.49% respectively. While the proportion of births to mothers with late or no prenatal care was 3.49% for the whole US, the West presented a significantly higher percentage (4.42%). Findings from the spatial analysis mirror statistical results. Implications: Findings suggest any attempt to assess the relationship between population variables and birth outcomes should account for regional differences.