Recent declines in New York City infant mortality rates

Area of Science:

• Public Health
• Epidemiology
• Biostatistics

Background:

• Infant mortality rates in New York City (NYC) have historically declined.
• A significant acceleration in this decline was observed starting in the late 1980s.

Purpose of the Study:

• To analyze the accelerated decline in infant mortality across racial/ethnic groups in NYC.
• To determine the relative contributions of changes in birth weight distribution versus birth weight-specific death rates to this decline between 1988-1989 and 1992-1993.

Main Methods:

• Utilized linked birth and death certificate files for two NYC birth cohorts (1988-89 and 1992-93).
• Employed multinomial logistic regressions stratified by race/ethnicity to assess neonatal and postneonatal mortality probabilities.
• Applied direct and indirect standardization to isolate the impact of birth weight distribution and birth weight-specific death rates.

Main Results:

• Infant mortality rates decreased by 27.4% (whites), 24.8% (Hispanics), and 22.7% (blacks).
• Declines in birth weight-specific death rates were the primary driver of reduced infant mortality, outweighing improvements in birth weight distribution.
• Normal birth weight infants (>2500g) showed the most significant improvements in mortality rates across all racial/ethnic groups.

Conclusions:

• The accelerated decline in NYC infant mortality from 1988-1989 to 1992-1993 was mainly due to lower birth weight-specific death rates.
• Improvements in the overall birth weight distribution of the population were not the primary factor.
• Normal birth weight infants experienced the most substantial gains in survival during this period.