Substance use during pregnancy is a public health concern that has potential short- and long-term effects for infants and young children. Ongoing parental substance abuse and the home environment have significant consequences for infant and child development. Pregnancy may be an ideal time to address maternal substance abuse; however, early detection of prenatal substance use is complicated by a number of political/legal, economic, and social/attitudinal barriers. Addressing the needs of substance-exposed infants requires coordination of prevention (education and screening) and early intervention by multiple agencies, including child welfare. This article focuses on early detection of prenatal substance abuse, with attention to the role of the child welfare field. The article reviews the policy context for early detection and presents the results from a review of screening instruments for detecting substance use in pregnant women. The article concludes with a discussion of the implications of the findings for collaboration between programs and child welfare practice.