Abstract 32

Objective: To examine the population level impact of improved respiratory care on US neonatal mortality. Methods: All live births weighing ≥ 500 grams in 1985-91 U.S. birth cohorts (27,578,316 live births, 128,329 neonatal deaths) were examined for secular trends in birth weight and cause-specific neonatal mortality rates (NMR). Sixty-one underlying causes of death were used to study the trends in three categories of respiratory related causes of death and a fourth category of non-respiratory deaths. The four groups were comprised of: 1) RDS alone; 2) Primary atelectasis and RDS complications (pneumothorax, interstitial emphysema, and chronic lung disease); 3) Aspiration syndromes, congenital pneumonia, and acquired or unspecified respiratory diseases; 4) Non-respiratory causes of deaths. NMR is defined as number of deaths under 28 days per 1000 live births. Results: Overall NMR was significantly reduced by 12% between 1985 (5.4/1000) and 1988 (4.7/1000), and by 26% between 1988 (4.7/1000) and 1991 (4.0/1000). Rates of decline in the respiratory and non-respiratory causes of death were comparable between 1985 and 1988. However, from 1988 to 1991, the declines in cause-specific NMRs were notably greater in all respiratory categories (38% in Group 1, 37% in Group 2, 39% in Group 3) than in the non-respiratory group (21% in Group 4). Decline in RDS deaths accounted for 23% and in all respiratory deaths for 40% of the total reduction in neonatal deaths between 1985 and 1991. Conclusion: Improvements in neonatal care for respiratory diseases in recent years and particularly since 1988 have contributed significantly to reductions in the U.S. neonatal mortality.