Why are neonatal mortality rates lower in small black infants than in white infants in similar birth weight?

Abstract

PERINATAL MORTALITY DATA from the United States indicate that low-birth-weight Afro-American neonates are more likely to survive the neonatal period than are white infants of similar birth weight. Data illustrating this phenomenon are shown in Table I. Analyses in the original publication of these data' indicate that differences in gestational age do not explain the higher survival rates of small black neonates; neonatal mortality rates for black infants are lower than those for white infants at each gestational age at all birth weights less than 3,000 gm. This study was undertaken to explore whether this observed difference is due to characteristics associated with the lower socioeconomic status of blacks in American society. We hypothesized (1) that the factors which lead to low birthweight in a population of low socioeconomic status might be different from those that lead to low birth weight in a population of higher socioeconomic status, (2) that these factors might be less noxious in terms of neonatal survival, and (3) that a higher incidence of infants whose low birth weight was associated with these less noxious factors might explain the higher survival rates of low-birth-weight black American neonates. To test this hypothesis we compared the survival of lowbirth-weight infants born at Magee Women's Hospital between 1971 and 1974. We utilized care by a private attending obstetrician as an indicator of socioeconomic status in comparing the neonatal survival of black and white live-born infants. As shown in Table II, in almost every low-birth-weight category black infants were more likely to survive than