International comparisons of infant mortality and related factors: United States and Europe, 2010.

OBJECTIVES This report investigates the reasons for the United States' high infant mortality rate when compared with European countries. Specifically, the report measures the impact on infant mortality differences of two major factors: the percentage of preterm births and gestational age-specific infant mortality rates. METHODS Infant mortality and preterm birth data are compared between the United States and European countries. The percent contribution of the two factors to infant mortality differences is computed using the Kitagawa method, with Sweden as the reference country. RESULTS In 2010, the U.S. infant mortality rate was 6.1 infant deaths per 1,000 live births, and the United States ranked 26th in infant mortality among Organisation for Economic Co-operation and Development countries. After excluding births at less than 24 weeks of gestation to ensure international comparability, the U.S. infant mortality rate was 4.2, still higher than for most European countries and about twice the rates for Finland, Sweden, and Denmark. U.S. infant mortality rates for very preterm infants (24-31 weeks of gestation) compared favorably with most European rates. However, the U.S. mortality rate for infants at 32-36 weeks was second-highest, and the rate for infants at 37 weeks of gestation or more was highest, among the countries studied. About 39% of the United States' higher infant mortality rate when compared with that of Sweden was due to a higher percentage of preterm births, while 47% was due to a higher infant mortality rate at 37 weeks of gestation or more. If the United States could reduce these two factors to Sweden's levels, the U.S. infant mortality rate would fall by 43%, with nearly 7,300 infant deaths averted annually.