Decrease in infant mortality in New York City after 1989.

OBJECTIVES: This study identified factors contributing to the rapid decline in infant mortality in New York City from 1989 to 1992. METHODS: Changes in birthweight distributions and in birthweight/age-, cause-, and birthweight/age/cause-specific mortality rates from 1988/89 (before the mortality reduction) to 1990/91 were identified from New York City vital statistics data. RESULTS: Infant, neonatal, and postneonatal mortality of very-low-birthweight (< 1500 g) and normal-birthweight infants decreased significantly. The declines were almost entirely due to decreases in birthweight-specific mortality rates, rather than increased birthweights. All races experienced most of these reductions. Mortality decreased significantly for 6 causes of death. These decreases were consistent with the birthweight/age groups experiencing mortality declines. CONCLUSIONS: Widespread, multiple perinatal and postnatal factors contributed to the decline in infant mortality.