Examined effects of prenatal drug exposure on infants born preterm and full-term to African American mothers. Found more extreme fetal growth deficits in later-born infants, and more extreme irritability increases in earlier-born infants. Gestation length did not moderate cardiorespiratory reactivity effects. Exposure effects occurred for cocaine-polydrug and alcohol-only users and could be unambiguously attributed to either drug alone. (Author)