From the perspective of investigators conducting research involving pregnant women and fetuses, a woman's decision about whether to have an abortion can sometimes be relevant to the suitability of the woman and fetus as research subjects. However, prominent ethicists disagree over whether it is permissible for a woman's decision about abortion to be an inclusion or exclusion criterion for participation in research. A widely held view is that fetuses to be aborted and fetuses to be carried to term should be treated equally as research subjects. Some hold that this principle implies that a woman's decision about whether to have an abortion should not be an inclusion or exclusion criterion. This paper identifies types of research in which investigators might want to have inclusion or exclusion criteria based on decisions about abortion. It examines the arguments for and against having the woman's decision about abortion included in such criteria. It is argued that there are types of research in which such criteria are ethically permissible.