Neonatal mortality risk in relation to birth weight and gestational age: update.

Neonatal mortality risk for all birth weight-gestational age categories has been prepared based on data from an inborn population at the University of Colorado Health Sciences Center for the years 1974 to 1980. There were 14,413 live births and 252 neonatal deaths during this six-year period, reflecting fairly current clinical practices. Based on birth weight alone, neonatal mortality was 0.47% for infants weighing greater than 2,500 gm; based on gestational age alone, mortality was 0.28% for infants greater than 34 weeks. A chart of neonatal mortality risk has been constructed based on birth weights and gestational ages of all these infants. The zones of mortality risk have been color matched to equivalent areas of mortality for the 1958 to 1969 data previously published from the Center for easy comparison. These two populations have also been compared on a graph plotting the predicted mortality at the estimated gestational age and its fiftieth percentile birth weight. This may be useful for consultation by perinatal obstetricians who must make decisions about transfer and care of high-risk mothers before delivery occurs. Where comparisons can be made with other perinatal centers, there is a remarkable similarity in neonatal survival rates, indicating that continuing communication between obstetric perinatologists and neonatologists is a prime factor in reducing mortality, rather than specific new therapeutic procedures at any single clinical center.