The differential effect of traditional risk factors on infant birthweight among blacks and whites in Chicago.

We analyzed 103,072 White and Black births in Chicago from the 1982 and 1983 Illinois vital records, using 1980 median family income of mother's census tract as an ecologic variable. Thirty-one percent of Blacks and 4 percent of Whites resided in census tracts with median family incomes less than or equal to $10,000/year. Only 2 percent of Black mothers, compared to 16 percent of White mothers, lived in areas where the median family income was greater than $25,000/year. Among Blacks with incomes less than or equal to $10,000/year, maternal age, education, and marital status had minimal predictive power on the incidence of low birthweight (LBW) infants. Among high-risk mothers in the poorest areas the proportion of LBW infants in Blacks and Whites was less divergent than in higher income areas. Independent of residential area, low-risk Whites had half the occurrence of LBW infants as Blacks. We conclude that the extremes of residential environments show dramatic racial disparity in prevalence, yet the few low-risk Blacks still do less well than low-risk Whites. Traditional risk factors do not completely explain racial differences in neonatal outcome.