David R J, Siegel E
Pediatrics. 1983 Apr;71(4):531-40.
A state's declining neonatal mortality rate was studied over the decade 1968 to 1977 to determine how much of the decrease resulted from improved risk characteristics in the newborn population. A shift was found over time, mostly among white births, toward higher birth weights and longer gestations. Overall, there was a 19% reduction in the low-birth-weight rate. Considerable improvement in birth weight-specific mortality was also found, especially in babies weighing 1,000 to 2,500 g during the last 5 years of the study. A neonatal risk matrix model was applied to the changes over time to separate the improvement due to shifts in population risk characteristics from that due to better care of the newborn. Thirty-four percent of the decade's decrease in NMR was attributable to changes in the birth weight and gestational age makeup of the newborn population. This "better babies" component was more prominent early in the decade and among the white population.
对1968年至1977年这十年间一个州新生儿死亡率的下降情况进行了研究，以确定下降中有多少是由于新生儿群体风险特征的改善所致。随着时间的推移，发现出生体重增加和孕期延长的情况有所变化，这种变化主要发生在白人新生儿中。总体而言，低体重出生率下降了19%。还发现出生体重特异性死亡率有显著改善，尤其是在研究的最后五年中体重为1000至2500克的婴儿中。应用新生儿风险矩阵模型对随时间的变化进行分析，以区分因人群风险特征变化导致的改善和因对新生儿护理更好导致的改善。该十年间新生儿死亡率下降的34%归因于新生儿群体出生体重和胎龄构成的变化。这种“更健康的婴儿”因素在该十年早期以及白人人群中更为突出。
