A comparison of recent trends in infant mortality among twins and singletons

Overall infant mortality rates have steadily declined in recent years. The goal of this study was to examine whether recent declines in infant mortali ty were similar for twins and singletons, and to assess the impact of diffe ring birthweight distributions on these relationships. Linked birth and inf ant death records for 1985-86 and 1995-96 were used to calculate infant mor tality rates for twins and singletons for the two time periods. Bootstrap s imulations were used to estimate rates of decrease between the two time per iods and to determine whether these rates differed between twins and single tons. Between 1985-86 and 1995-96, infant mortality among twins declined si gnificantly faster than among singletons (36% vs. 29%, P < 0.05). This diff erence was true for both black and white infants (black: 28% for twins vs. 22% for singletons; white: 38% for twins vs. 31% for singletons). Within bi rthweight categories, infant mortality declined more rapidly among twins th an among singletons, although differences were not always significant. Fact ors and circumstances that contributed to the infant mortality decline in t he United States have benefited twins to a greater extent than singletons.