Rising infant mortality in Delaware: An examination of racial differences in secular trends

Objectives: Recent increases in the Delaware Infant Mortality Rate (IMR) have been attributed to a rise in the mortality of very low birth weight (VLBW, <1500 g) infants born to mothers of higher socioeconomic status. This study examines whether the determinants of infant mortality trends in Delaware vary by race. Methods: Linked birth/infant death cohort files for the two periods 1993-1997 and 1998-2002 were used to evaluate the determinants of infant mortality trends separately for White and Black racial groups. Kitagawa analyses determined the components of race-specific infant mortality trends attributable to changes in both the birthweight distribution and birthweight-specific mortality rates. Maternal characteristics were examined to identify factors associated with IMR changes. Results: Between the two time periods, infant mortality increased 23% among White infants and 17% among Black infants. For both races, the infant mortality increase was explained by increases in the incidence and mortality of VLBW infants, specifically below <500 grams for Blacks and <1,000 grams for Whites. The increased incidence of VLBW deliveries was statistically significant only among Whites, almost 40% of which was explained by an increase in multiple births. For both Whites and Blacks, the increase in VLBW mortality occurred mainly among births to more traditionally advantaged women who were twenty or older, at least high school educated, married, privately insured, had received first trimester prenatal care, and those who delivered multiple births. Conclusions: These findings suggest that conventional strategies of increasing access to prenatal care among disadvantaged women may be insufficient to reverse recent IMR increases in Delaware, irrespective of race. Future efforts should focus on understanding the causes of the increased infant mortality associated with higher socioeconomic status, including changes in assisted reproductive technology utilization, maternal health status, and obstetric practice.