Child maltreatment is associated with increased risk of substance abuse in adulthood. However, prior investigations have not examined substance use specifically in pregnancy and have relied on self-report of substance use. The present study addresses these gaps via secondary analysis of 295 primarily low-income, Black postpartum women who agreed to complete a brief questionnaire and subsequently provided urine and hair samples. A clear relationship emerged between self-reported maltreatment and positive toxicology (with drug use present in 37.2% of maltreated participants and 17.1% of nonmaltreated participants; p < 0.001). Depression and violence exposure were positively associated with maltreatment and with drug use. The combined effect of violence exposure and depression mediated the association between maltreatment and drug use during pregnancy. (The bootstrapped 95% confidence interval of total indirect effect ranged 0.14-0.80.) This investigation is the first to show an association between childhood maltreatment and toxicological evidence of drug use in pregnancy.