Vulnerability is an important factor to be considered with regard to the selection of subjects. Examples of groups who are customarily considered vulnerable include children, pregnant women (when considered with regard to the vulnerability of the fetus), decisionally impaired persons, and prisoners. In addition other populations, such as students, employees, the seriously ill, the terminally ill, and the dependent or impoverished may also be considered vulnerable. If vulnerable subjects are to be included in a research study, special protections must be incorporated into the protocol. Please see the Vulnerable Subjects module for further information on this topic.