Changes in infant morbidity associated with decreases in neonatal mortality.

Neonatal mortality and morbidity among infants surviving to 1 year of age in eight geographic areas have been compared to determine whether recent decreases in mortality have affected the risk of infants having congenital anomalies or developmental delay. Mortality was obtained from birth and death records in 1976 and either 1978 or 1979; morbidity through home interviews with mothers of random samples of infants and developmental observations on the children. It is concluded that the decrease in mortality was not offset by increases in children with defects. Neonatal mortality decreased by 18% in this 2- to 3-year period; risk of congenital anomalies or developmental delay (all types combined) declined by 16% among the surviving infants. The reduction in risk was concentrated in the minor congenital anomalies or developmental delay category; the proportion of children with severe or moderate congenital anomalies or developmental delay did not change. Decreases occurred at every birth weight including the very low birth weights of 1,500 g or less, a subgroup with especially high mortality and morbidity resulting from perinatal events.