BACKGROUND: The relationship between non-Hispanic White (NHW) women's decreased neighborhood income between early-life and adulthood, individual risk-status at delivery, and small for gestational age (weight for gestation < 10th percentile, SGA) rates is unknown. OBJECTIVE: To determine the extent to which NHW women's exposure to decreased neighborhood income is a risk factor for SGA births, and whether their own birth weight modifies this relationship. METHODS: Stratified and multilevel logistic regression analyses were executed on the Illinois transgenerational dataset of mothers (born 1956-1976) and their infants (born 1989-1991) with appended U.S. census income information. Only NHW women with an early-life residence in top income quartile Chicago neighborhoods were studied. RESULTS: NHW women (n = 4889) unexposed to decreased neighborhood income between early-life and adulthood had an SGA rate of 7.1%. In contrast, NHW women exposed to slightly (n = 5112), modestly (n = 2158), or severely (n = 339) decreased neighborhood income by the time of delivery had SGA rates of 8.2%, 10.8%, and 10.8%, respectively; RR (95% CI) equaled 1.2 (1.0-1.3), 1.5 (1.3-1.8) and 1.5 (1.1-2.1), respectively. The relationship between maternal exposure to modestly decreased neighborhood income and SGA rates was present only among former non-low birth weight (> 2500 g, non-LBW) mothers. In multilevel logistic regression models, the adjusted (controlling for age, parity, prenatal care usage, and cigarette smoking) OR of SGA birth for former low birth weight (< 2500 g, LBW) and non-LBW NHW women exposed to modestly (compared to no) decreased neighborhood income equaled 0.7 (0.4, 1.4) and 1.3 (1.1-1.6), respectively. CONCLUSIONS FOR PRACTICE: NHW women's exposure to modestly decreased neighborhood income is associated with an increased risk of SGA birth; this phenomenon is absent among former low birth weight women.