Risk factors and 1999-2001 infant mortality among White and Black singletons in the United States

We evaluate the joint effects of social, demographic, and medical risk factors on infant mortality among US non-Hispanic White and non-Hispanic Black singletons using the 1999-2001 linked birth/infant death datasets. A three-step statistical analysis on 6,732,344 singletons identifies low birth weight, pre-term birth, pregnancy-associated hypertension and hydramnios/oligohydramnios during pregnancy as the most significant risk factors for infant mortality. Other predictors include maternal education, maternal tobacco use, infant gender, infant race, adequacy of prenatal care, incompetent cervix, eclampsia, chronic hypertension, Rh sensitization, and uterine bleeding during pregnancy. County-level variations quantified in the multi-level nonlinear logistic regression were significant. The county-level analysis shows that infant mortality within a county was highly correlated with Gini index, median household income, poverty percent and White-Black population ratio.

Three-year infant mortality rate among the Blacks (10.13%) was more than twice the rate among Whites (4.29%). Subgroup analysis by race reveals that Blacks had lower average birth weight, lower average maternal age, less education, larger proportions of pre-term births and unmarried mothers; Whites had larger proportions of maternal tobacco use and alcohol use. Prenatal care among Whites was better than that in Blacks. Single-level multivariable analyses show that predictors of infant mortality may differ by race and the contribution of medical risk factors was higher among blacks when compared to their white counterparts. Further exploration of neonatal infant mortality among four race-gender subgroups implies that the Black males had the worst survival, while White males appeared to have the best survival during the neonatal period.