Infant mortality rate (365d, IMR) of term (37-42 wks) non-Latino Whites, African-Americans, and Mexican-Americans: What's maternal nativity got to do with it?

Background: US-born African-American and Mexican-American women have greater rates of preterm birth and consequent overall infant mortality than their foreign-born peers. However, the relation of maternal nativity to the IMR of term White, African-American, and Mexican-American infants is unknown. Objective: To determine whether maternal birth in the US is a risk factor for first year mortality among term White, African-American, and Mexican-American infants. Methods: Race/ethnic group-specific stratified and multivariable binomial regression analyses were performed on the 2003-2004 National Center for Health Statistics linked live birth-infant death cohort files. Only term non-Latino White, African-American, and Mexican-American infants were studied. Maternal variables examined included nativity, age, education, marital status, parity, prenatal care usage, and region of birth. Results: The IMR of White infants with US-born mothers (N=3,684,569) exceeded that of White infants with foreign-born mothers (N=226,621): 2.4/1,000 vs. 1.3/1,000, respectively; RR = 1.8 (1.6-2.0). Most striking, the maternal disparity in IMR among Whites persisted across all measured covariates. In a multivariable binomial regression model, the adjusted RR of infant mortality for US-born (compared to foreign-born) White mothers equaled 1.5 (1.3-1.6). Similarly, the adjusted RR of infant mortality for US-born (compared to foreign-born) African-American and Mexican-American women were 1.5 (1.3-1.7) and 1.5 (1.3-1.6), respectively. No singular cause of death explained these phenomena. Conclusions: Maternal birth in the US, or something closely related to it, is a risk factor for first year mortality among term non-Latino White, African-American, and Mexican-American infants. Greater research and public health attention to this epidemiologic enigma is warranted.