Sudden infant death trends in six metropolitan communities, 1965-1974.

Data from six geographically dispersed metropolitan areas in the United States in which special sudden infant death syndrome (SIDS) surveillance programs for detection and autopsy diagnosis existed during the period 1965 through 1974 reveal considerable diversity in overall ten-year incidence rates as well as in annual rate distribution patterns. A downward trend in SIDS incidence occurred in some areas but not in others. Non-SIDS postneonatal death rates, which were used for comparison, also decreased in some areas. Rate trends for whites and nonwhites were not consistent. During the same period, the fertility rate in the United States decreased by about a third for both whites and nonwhites. To explain the observed trends we postulate that concomitants of the fertility rate decline may have reduced the number of "high mortality risk babies" to a variable degree in different places and at different times.