**5. Conclusions**

Prenatal drug exposure is a risk factor for increased vulnerability to difficulties in both behavior and cognition. Continued research to identify the structural and functional targets of prenatal drug-related neurotoxicity is important. Identifying biomarkers of prenatal drugrelated changes in brain development and relating those changes to behavior, or in the case of alcohol to physical features, has the potential to inform diagnostic and treatment strategies. MRI, fMRI, and DTI neuroimaging methods provide powerful tools for visualizing the brain and, because they are noninvasive, are especially suited for research in young children. The impact of prenatal drug exposure on brain structure and function is subtle and often ac‐ count for a small amount of variance that contributes to deficits in behavior regulation and cognition. These subtle effects can be explained by the complex interactions of the pattern of prenatal drug exposure both in terms of the timing and dose as well as the combination of multiple drugs, genetic, and environmental factors. Changes in brain structure and function in children and adolescents with prenatal drug exposure can be difficult to assess for a number of other reasons. To date, a neuropsychological profile for prenatal drug-related deficits in cognitive function has not been identified and there are diffuse individual differences in the expression of the impact of prenatal drug exposure on the brain and behavior. Furthermore, limitations in statistical approaches to the analysis of neuroimaging data can often lead to difficulty in detecting these subtle effects. Future studies will require large sample sizes and longitudinal research designs, and increasingly sophisticated neuroimaging and statistical methods. A focus on connectivity measures will provide a better understanding of underly‐ ing mechanisms for the associations between brain structure and function, and behavior.
