Small for gestational age (weight for gestational age <10th percentile, SGA) birth status and adulthood susceptibility to diabetes is well established, but the relationship to diabetes during pregnancy is incompletely understood. The authors investigated the association between women's impaired fetal growth (as measured by SGA status) and diabetes mellitus (DM) during pregnancy. Stratified and multivariable binomial regression analyses were performed on the Illinois transgenerational dataset. Former SGA (n = 13,934) mothers had a greater prevalence of DM during pregnancy than former appropriate for gestational age (AGA) mothers (n = 116,683): 2.7 versus 1.9 %, relative prevalence (RP) equaled 1.4 [95 % confidence interval (CI)1.3, 1.6]. In a multivariable binomial regression model, the adjusted RP (95 %CI) (controlling for maternal age, education, parity, plurality, marital status, and race/ethnicity) for DM during pregnancy for former SGA (compared to AGA) mothers equaled 1.5 (1.3, 1.6). When stratified by race/ethnicity, the adjusted RP (95 % CI) of DM during pregnancy for former SGA (compared to AGA), non-Latina White, African-American, and Mexican-American mothers was 1.4 (1.3, 1.6), 1.6 (1.2, 2.1), and 2.3 (1.1, 4.7), respectively. The authors conclude that impaired fetal growth (as measured by SGA status) is a risk factor for DM during pregnancy among the leading racial/ethnic groups in the United States.