Advancing maternal age and infant birth weight among urban African Americans: the effect of neighborhood poverty.

OBJECTIVE: This study sought to determine whether neighborhood poverty modifies the relationship between maternal age and infant birth weight among urban African Americans. DESIGN: Stratified analyses were performed on the vital records of African Americans born in Chicago by means of 1992-1995 computerized birth file with appended 1990 US Census income and 1995 Chicago Department of Public Health data. Four neighborhood-level variables (low median family income, high rates of unemployment, homicide, and lead poisoning) were analyzed. SETTING: This is a population-based study. RESULTS: Twenty-one percent (n=21,811) of women resided in nonimpoverished neighborhoods (zero ecologic risk factors); 23% (n=24,914) of women lived in extremely impoverished neighborhoods (four ecologic risk factors). In nonimpoverished neighborhoods, 30-34 year old women had a moderately low birth weight (1500-2499 g) rate of 13.9% compared to 10.3% for women aged 20-24 years; risk difference (95% confidence interval [CI])=3.5 (2.2-4.6). In contrast, extremely impoverished women aged 30-34 years had a moderately low birth weight rate of 19.8% compared to 11.8% for women aged 20-24 years; risk difference (95% CI)=7.7 (6.1-9.3). This trend persisted among women who received early prenatal care and were primagravids or of low parity. Neighborhood poverty did not modify the association of advancing maternal age and the risk of very low birth weight (<1500 g). CONCLUSIONS: Neighborhood poverty accelerates the rise in moderately low birth weight but not very low birth weight; rates were associated with advancing maternal age among urban African Americans.