Infant mortality: explaining black/white disparities in Wisconsin

Understanding the factors contributing to black/white disparities in infant mortality rates in Wisconsin is a prerequisite to decreasing these disparities and improving birth outcomes. We examined multiple determinants of infant mortality to understand the impact of specific risk factors on the infant mortality rates of blacks and whites in Wisconsin.

We used the Wisconsin Interactive Statistics on Health database to examine infant mortality data for the 5-year time period, 1998-2002 (N=32,166 black infant births; 272,559 white infant births). We conducted a bivariate analysis of relative risks (RR) of infant mortality (black vs. white) using specific variables available in the database. We then examined the relationship between infant mortality rate and selected risk factors using regression analyses.

Unadjusted, black infants were 3.0 times more likely to die during their first year of life, compared with white infants. Adjusting for gestational age black infants were only 1.9 times more likely to die. The risk was further reduced, after adjusting for birth weight, to 1.3. However, stratifying and adjusting for 8 other multiple variables accounted for some, but not all of the disparity. Black infants who had the same risk profile as white infants still had a 2-fold excess risk of death. In addition, simultaneously controlling for 4 of the 8 risk factors (maternal age, maternal education, adequacy of prenatal care received, and region of the state) also reduced, but did not eliminate, this excess risk (RR was still 2.2 for black infants). Independent of maternal age and region of the state, adequate prenatal care and higher levels of education are significant indicators of the racial disparity between whites and blacks.

These results suggest that, within a given racial group, increasing access to prenatal care and increasing maternal educational attainment will improve infant mortality rates but will not eliminate the black/white disparity in infant mortality. In fact, these interventions may actually widen the disparity in infant mortality rate between blacks and whites, especially if funds and programs are applied equally throughout the population, rather than targeted to high-risk individuals, who lag significantly behind the majority population. The Wisconsin white population, which has already attained an infant mortality rate of 4.5 per 1,000 live births, will continue to have greatest benefit from these programs compared to blacks who have a rate of 19.2 in 2004; thus, the disparity is not eliminated and the gap widens probably due to differential uptake of health messages secondary to health literacy issues. Further research is needed to fully understand the additional, more difficult to measure factors that contribute significantly to infant mortality, especially among black women.