Changes in the black-white infant mortality gap from 1983 to 1991 in the United States

Background: The long-standing difference in infant mortality in the United States between black and white infants has increased in recent years. To help identify the cause, we evaluated changes in birthweight distributions (BDs) and birthweight-specific mortality rates (BSMRs) among black and white infants born in the United States between 1983 and 1991. Methods: Using national linked birth and death certificate data, we limited analyses to singleton births that occurred in the United States to resident, non-Hispanic black and white women. Birthweight data were analyzed in 500 g increments. The black-white gap was partitioned into deaths due to differences in BDs and BSMRs. Results: The black-white infant mortality rate ratio increased from 2.1 in 1983 to 2.4 in 1991. Decreases in BSMRs among infants weighing from 500 to 2499 g occurred in both groups but were smaller among black than white infants; consequently, the percentage of excess deaths to black infants due to differences in BSMRs almost doubled during the study period, from 6.5% to 11.9%. Rates of very low birthweight (VLBW, <1,500 g) increased for black infants, but the ED for white infants changed little. Although about 90% of the excess deaths to black infants resulted from differences in BDs, the changes in BDs had a minimal effect on the widening infant mortality gap. Conclusions: A significant reduction in the black-white infant mortality gap will require a reduction in VLBM and low birthweight (LBW, <2,500 g). To keep the gap from growing, we must also investigate why decreases in BSMRs were smaller among black than white infants between 1983 and 1991.