A Multicenter Study of Preterm Birth Weight and Gestational Age-specific Neonatal Mortality

Objective: This analysis was performed to present updated neonatal mortality data by age and birth weight for preterm newborns and to demonstrate the influence of plurality, ethnicity, and infant sex on mortality.

Study Design: Preterm birth weight and gestational age-specific mortality rates were compiled from the five centers that participated in the March of Dimes Multicenter Preterm Birth Prevention Project. In each center gestational age was assessed by standardized methods. A birth weight and gestational age-specific mortality chart for preterm births was created with live-birth data.

Results: In each birth weight group mortality decreased as the gestational age advanced; for each gestational age group heavier infants had less mortality. Female infants < 29 weeks survived better than male infants, and singletons < 29 weeks survived better than twins. Survival for black preterm newborns was better than that of whites but differences were not significant. Mortality for black term infants was significantly higher. The largest improvement in survival occurred between 25 and 26 weeks. At 30 weeks survival was > 90% and improved < 1% per week thereafter.

Conclusions: When compared with rates in previous reports, mortality rates appear to have improved, especially at gestational ages < 29 weeks. These data may be useful in decision-making and in counseling patients at risk for preterm delivery.