The sample size of the studies (total of exposed and comparison groups) also varies by drug of interest. Studies examining cocaine exposure have sample sizes ranging from 22-60, methamphetamine 26 and 28, and the marijuana studies range from 11-31. Among the alcohol studies, there is one cohort of 90152 with the rest of the studies ranging from samples of 2162 - 45153. The prenatal tobacco exposure studies include samples of 181194 300190 and 31498. By contrast, most studies of the behavioral consequences of prenatal drug exposure are conducted on larger samples. A recent review of the prenatal cocaine exposure literature indicated that more than half of the long term follow-up studies included samples of at least 300 with a maximum of 1,000203. Therefore, we probably have more confidence in the behavioral findings than in the neuroimaging findings at this time point. Advances in technology including both the software and hardware available on newer MR imaging platforms, as well as the software and data processing pipelines evolving for the rapid and unbiased analysis of MR-derived data hold promise for the near
